question

Preanalytical and susceptibility Testing

Proper media for culture of a urethral drainage from a man include:

answer

Chocolate and modified Thayer Martin agars

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A sheep blood agar plate inoculated with 0.001 mL of urine grows 70 colonies of Staphylococcus aureus. How many colony forming units per mL of urine should be reported?

answer

70,000

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The lowest concentration of antibiotic that inhibits growth of a test organism is the:

answer

minimum inhibitory concentration.

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Which of the following clean catch urine culture colony counts indicates the patient likely has a urinary tract infection?

answer

10³ CFU/mL

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the steam autoclave method of sterilization:

answer

uses 15 lbs of pressure for 15 mins

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The expected colony count in a suprapubic urine from a healthy individual is:

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0 CFU/mL

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An aspirate of a deep wound was plated on blood agar plates and incubated aerobically and anaerobically. At 24 hours there was growth on both plates. This indicates that the organism is a:

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facultative anaerobe

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The proper blood to broth ratio for blood cultures to reduce the antibacterial effect of serum in adults is:

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1:10

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A penicillin-resistant Neisseria gonorrhoeae produces:

answer

beta-lactamase

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Which selective medium is used for the isolation of gram positive microorganisms?

answer

Columbia CNA with 5% sheep blood

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The most sensitive substrate for the detection of beta-lactamases is:

answer

nitrocefin
The chromogenic cephalosporin test using nitorcefin is the most sensitive and specific test for the detection of beta lactamase.

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A Staphylococcus aureus isolate has an MIC of 4 ug/mL to oxicillin.There is uncertainty as to whether this represents an oxacillin (heteroresistant) resistant strain or a hyperproducer of beta-lactamase.
Strain          Oxacillin          Amoxicillin-clavulanic acid
strain A         susceptible       susceptible
strain B          susceptible       resistant
strain C          resistant            susceptible
strain D           resistant            resistant
Based on the above results for oxacillin and amoxicillin-clavulanic acid, which is heteroresistant

answer

Strain D

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An enterococcus isoloted from multiple blood cultures in a patient with endocarditis should be:

answer

screened for high level aminoglycoside resistance

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In the Kirby-Bauer disc diffusion susceptibility test, which variable is critical when testing Pseudomonas species for antibiotic sustibility to amosides?

answer

cation content of the media
(Ph)

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The procedure that assures the most accurate detection of mec-a mediated oxacillin resistance in routine broth microdilution susceptibility testing against S. aureus is:

answer

use of cefoxitin for testing

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Three sets of blood cultures were obtained from an adult patient with fever and suspected endocarditus. The aerobic bottle of one set had growth of staphylococcus epidermidis at 5 days of incubation. This indicates that:

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The organism is most likely a contaminant

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Susceptibility testing performed on quality control organisms using a new media lot number yielded zone sizes that were too large for all antobiotics tested. The testing was repeted using media from a previously used lot number, and all zone sizes were acceptible. Which of the following best explaines the unacceptable zone sizes?

answer

The depth of the media was too thin

question

When performing a stool culture, a colony type typical of an enteric pathogen is subcultured on a blood agar plate. The resulting pure culture is screened with several test to obtain the following resilts:
TSI: acid butt, alkaline slant, nogas, no H2S
phenylaninine deaminase: negative
motility: positive
serology typing: (shigella subgroup B)
The serological typing is verified with new kit and controls. The best course of action would be to:

answer

Verify reactivity of motility medium with positive and negative controls.

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In order to isolate Camoylobacter coli/jejuni the fecal specimen should be:

answer

inoculated onto selective plating media and incubated in reduced oxygen with added CO₂ at 42*C
(micraerophillic atmosphere and selective media are needed for Campylobacter)

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An expectorated sputum is sent to the laboratory for culture from a patient with respiratory distress. The gram stain of the specimen shows many squamous epithelial cells (>/lpf) and rare neutrophlis. The microscope appearance of the organisms present include:
moderate gram positive cocci in chains and diplococci
moderate gram-negative diplococci
moderate palisading gram-positive bacilli
This Gram stain is most indicative of :

answer

oropharyangeal flora

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Which type of microscope would be most useful in examining viruses and the structure of microbial cells?

answer

electron

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After satisfactory performance of daily disk diffusion susceptibility quality control is documented, the frequency of quality control can be reduced to:

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every week

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In disc diffusion susceptibility testing, as antimicrobial agent diffuses away from the disk, the concentration of antibiotic is:

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decreased

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The most common cause for failure of a GasPac anaerobic jar to establlish an adequate enviroment for anaerobic incubation is:

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catalyst that have become inactivated after repeated use

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Which of the following is the most appropriate method for collecting a urine specimen from a patient with an indwelling catherter?

answer

aspirate urine aseptically from the catheter tubing.

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Which of the following specimen request is acceptable?

answer

urine for culture of acid fast bacilli

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Which of the following groups of specimens would be acceptable for anaerobic culture?

answer

pleural fluid, brain abcess.

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A liquid fecal specimen from a three month old infant is submitted for microbiological examination. In addition to culture on routine media for Salmonella and Shigella, this specimen should be routinely:

answer

examined for the presence of Campylobacter sp

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Cerebrospinal fluid from a febrile 25 year old man with possible meningitus is rushed to the laboratory for a stat Gram stain and culture.While performing the Gram stain, the technologist accidently spills most of the specimen. The smear shows many neutrophils and no microorganisms. Since there is only enough CSF to inoculate one plate, the technologist should usa a:

answer

chocolate agar plate

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A diabetic foot swab from a 82 year old woman with recurrent infections is submitted for culture. The Gram stain reveals:
many neutrophils, no squamous epithelial cells
many gram negative bacilli
many gram positive cocci in chains
The physican request that all pathogens be worked up. In addition to the sheep blood and MacConkey agar plates routinely used for wound cultures, the technologist might also process:

answer

a CNA agar plate

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Which of the following is the most appropriate specimen source and primary media battery?

answer

endocervical- chocolate, Martin Lewis

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Which of the following is the most appropriate organism and media combination?

answer

Yersinia enterocolitica- cefsulodin-irgasan-novibiocin (CIN)

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A Gram stain from a swab of a hand wound reveals:
moderate neutrophils
no squamous epithelial cells
moderate gram positive cocci in chains
moderate large gram negative bacilli
Select the appropriate media that will selectively isolate each organism.

answer

Columbia CNA, MacConkey

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Upon review of a sputum Gram stain, The technician notes that the nuclei of all of the neutrophils present in the smear are staining dark blue. The best explanation for this finding is:

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the slide was inadequately decolorized with acetone/alcohol

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When performing a Kovac indole test, the substrate must contain:

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tryptophan

The indole test is used for detrmining an organisms ability to produce indole from deamination of tryptophan.

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The ONPG test allows organisms to be classified as a lactose fermenter by testing for which of the following?

answer

beta-galactosidase
Through the action of the enzyme beta-galactosidase , ONPG cleaves into galactose and o-nitrophenol (a yellow compound)

question

Sodium bicarbonate and sodium citrate are componets of which of the following?

answer

JEMBEC system
The JEMBEC system is a transport and inoculation medium used for direct plating of specimens for N. gonorrhoeae. Chocolate- based selective medium is inoculated with the specimen. This is placed in an impermeable plastic bag with a bi-carbonate sodium citrate pellet that absorbs moisture to generate a carbon dioxide-rich envoroment.

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Chocolate agar base containing vancoumycin,
colistin, anisomycin, and trimethoprim is also known as:

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Martin Lewis agar

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A medium that aids in the presumptive identification of organisms based on their appearance on the medium is called:

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differential

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SPS is used as an anticoagulant for blood cultures because it:

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inactivates neutrophils and components of serum complement:

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When evluating a new susceptibility testing system, if the new system characterizes a susceptible isolate as resistant , this is termed a:

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major error

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Which of the following methods is inadequate for the detection of vancoumycin-intermediate S. aureus?

answer

disk diffusion.
The disk diffusion procedure will not differentiate S. aureus strains with reduced susceptibility to vancoumycin (MICs 4-8) from susceptible strains even when incubated for 24 hours.

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In the disk diffusion susceptibility test, which of the following can result if disks are placed on the inoculated media and left at room temperature for an hour before incubation?

answer

zones of larger diameter would result

a delay of more than 15 mins between placing the disks on the inoculated plate and incubation permits excess prediffusion of the antimicrobial agent from the disk. This would result in a larger than expected zone diameter.

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Which of the follwing factors would make an organism appear to be more resistant on a disk diffusion sustibility test?

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too many organisms in the innoculum

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First generation cephalosporins can be adequately repersented by:

answer

cephalothin
cefotetin and cefoxitin are second generation and ceftriaxone is a third generation.

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An antibiotic that inhibits cell wall synthesis is:

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penicillin

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Which one of the following organisms does not require susceptibility testing to the antimicrobial indicated when isolated from a clinically significant source.

answer

Streptococcus pyogenes-penicillin

susceptibility testing should be performed when susceptibility of the organism cannot be reliably perdicted and resistance is known or suspected. Susceptibilityntesting of penicillin for treatment of S pyogenes does not need to be performed routinely since resistance has not been documented.

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Which of the following antibiotics would routinely be tested and reported for isolates of Pseudomonas aruginosa?

answer

Gentamycin
(Gentamycin is an aminoglycoside)

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Which of the folllowing must be incubated in a microaerophilic enviroment for optimal recovery of the organism?

answer

Campylobacter jejuni

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Diagnosis of typhoid fever can be confirmed best by culture of :

answer

blood

The sensitivity of blood culture is 50-70%. Stool cultures are positive in < 50% of patients and urine cultures are positive even less frequently. Bone marrow has a sensitivity of up to 90%.

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Vibrio parahemolyticus can be isolated best from feces on:

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thiosulfate citrate bile salts (TCBS) agar

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Which of the following media can be used to culture Campylobacter jejuni?

answer

Skirrow medium

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Test for beta-lactamase in Heaemophilus influenza:

answer

should be performed on all blood and CSF isolates

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Media used to support growth of Legionella pneumophilia should contain which of the following additives?

answer

charcoal and yeast extract

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The best medium for culture of Bordetella pertusis is:

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Regan Lowe agar

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The best medium for Francesella tularensis is:

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Cystine glucose blood agar

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The most rapid method for detection of Francesella tularensis is:

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fluorescent antibody staining techniques on clinical specimens

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When processing throat swabs for group A Streptococcus culture, the medium of choice is:

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sheep blood agar

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The ability to detect oxacillin-resistant Staphylococcus aureus may be enhanced by:

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using Mueller-Hinton broth with 2% NaCl

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The optimal wound specimen for culture of anaerobic organisms should be:

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a syringe filled with pus; obtained before administration of antibiotics

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A 21 year old patient presents with pharyngitis. A throat swab is collected and submitted for anaerobic culture. This specimen should be:

answer

rejected as unacceptible
ananerobic bacteria do not cause pharyngitis

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Anaerobic sustibility testing is helpful in the management of patients with:

answer

synovial infections

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An antibiotic used to supress or kill contaminating fungi in media is:

answer

cyclohexamide

question

Production of beta-lactamase is inducible in which of the following:

answer

Staphylococcus aureus
Some bacteria such as Enterococcus sp, H. influenza and Neisseria gonorrhoeae continualy produce beta lactamase. S.aureus produces beta-lactamase only after exposure to an inducing agent (such as penicillin) C diptheriae and S. pyogenes do not produce beta lactamase.

question

[image]
A sputum specimen is recieved for culture and Gram stain. The Gram stain smear from this specimen seen in the image
The technologist best course of action would be to:

answer

Call the patient care area and request a new specimen.
here are several sputum screening systems for acessesing the quality of respiratory specimens. In general, neutrophils are a positive indicator of quality, and squamous epithelial cells are a negative indicator of quality, suggesting oropharyngeal contamination. This specimen contains an abundance of squamous cells, (>10/low power field), and would be unaccepitable for cultue.

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A technologist is reading a Gram stain from a CSF and observes many neutrophils and lancet shaped gram-positive diplococci. Which set of chemistry and hemotology CSF results would most likely be seen in someone with this type of infection?

answer

WBC increased, glucose decreased, Protein increased

question

Refer to the following:
                                   64    32    16        8         4          2     Control g/mL

gentamycin     Ο   Ο   Ο    Ο    Ο     Ο     positive

Examine the broth microdilution susceptibility test shown above and determine the MIC for Gentamycin.

answer

< 2 ug/mL

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Which of the following test is used to monitor bactericidal activity during antimicrobic therapy in cases of endocarditis?

answer

Schlicter
the serum bactericidal or Schlicter test can be used to acess the activity of patients serum when they are recieving long term therapy for endocarditis or osteomyelitis. High titers of anti bacterial activity in the serum suggest adequate dosing, a nontolerant isolate or normal elimination of the antibiotic.

question

Quality control results for disk diffusion susceptibility test yield the following results:
aminoglycoside zones too small and penicillin zones too large. This is most likely due to the:

answer

Ph of the Mueller-Hinton agar being too low

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When using a control strain of staphylococcus aureus, the technologist notices that the zone around the oxacillin disk is too small. Which of the following is the most likely explanation?

answer

use of outdated oxacillin disks

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In the disk diffusion method of determining antibiotic susceptibility, the size of the inhibition zone used to indicate susceptibility has been determined by:

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correlating the zone size with minimum inhibitory concentrations

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Which of the following organisms may be mistaken for Neissseria gonorrhoeae in Gram stained smears of uterine cervex exudates:

answer

Moraxella osloensis

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A 73 year old man diagnosed as having pneumococcal meningitis is not responding to his penicillin therapy. Which of the following test should be performed on the isolate to best determine this organisms susceptibility to penicillin?

answer

oxacillin disk diffusion
With the exception of the oxacillin disk screening test, disk diffusion is not recommended for testing S.pneumoniae aginst beta-lactam agents. S.pneumoniae does not produce beta-lactamase, so beta-latamase testing would not be useful

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Salmonella enteritidis is isolated from multiple blood cultures in a patient with fever. Susceptible results are as follows: ampicillin-susceptible, ceftriaxone- susceptible, ciprofloxacin-susceptible, trimethoprim/sulfamethoxazole-resistant. What is the next best step?

answer

Test the isolate aginst nalidixic acid and if resistant report the ciprofloxacin as resistant.

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Which of the following antimicrobials would be inappropriate to report on an E coli isolated from a wound culture

answer

nitrofurantoin
certian antimicrobials, such as nitrofurantoin and norfloxacin, are used only or primairly to treat urinay tract infections. These agents should not be reported for pathogens recovered from other sites of infections.

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The susceptibility results below are reported on an Enterococcus faecalis isolated from peritoneal fluid:
Ampicillin:     susceptible
vancoumycin: resistant
clindamycin; susceptible
levofloxacin:   resistant
linezolid: susceptible
The physican calls questioning the results. Which of the following should have been done before the report was called:

answer

The clindamycin result should have been removed from the report since it is inactive aginst enterococcus.

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A D test is performed on an isolate of Staphylococcus aureus to determine inducible clindamycin resistance:
[image]

answer

erythromycin resistant; clindamycin susceptible

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Which of the following combinations is useful for confirming the presence of extended spectrum beta-lactamase in E-coli?

answer

ceftazidime + clavulanic acid

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Enyzmatic drug modification is a mechanism of resistance for which antimicrobial

answer

gentamycin

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Which of the following is the most important variable in the recovery of organisms in patients with bacteremia?

answer

The volume of the blood cultured.

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A 24 year old man presents with pain on urination and urethral discharge. A gram stain of the discharge is seen in the image:[image]

answer

Neisseria gonorrhoae

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[image]A 10 year old child with cystic fibrosis persents with cough and shortness of breath. er sputum Gram stain is seen in this image:
Based on the gram stain what would be the best medium and incubation condition to optimze recovery of the organism seen?

answer

Chocolate agar incubated in CO₂

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[image]
The image depicts a Gram stain of a knee fluid from a patient who has recently undergone knee replacement surgery:

answer

Gram positive cocci suggestive of streptococcus

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A vaginal/rectal swab is collected from a pregnant patient to screen for group B streptococcus colonization. What is the best medium to use for the specimen inoculation?

answer

LIM broth

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A pregnant patient is screened at 36 weeks gestation for group B streptococccus (GBS). A vaginal swab is collected and cultured in Todd-Hewitt broth with 8 ug bentamicin /mL and 15 ug nalidixic acid/mL. The broth is subcultured onto sheep blood agar after 24 hours incubation. No GBS are seen on the subculture and the results are negative. The patient later goes on to deliver an infant wiith early onset GBS disease. What is the most likely reason for the negative GBS culture?

answer

A vaginal swab was collected instead of a vaginal/rectal swab

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Susceptibility testing is performed on a Staphylococcus aureus isolate from a blood culture with the following results:
oxacillin:     resistant
cefazolin:    susceptible
Clindamycin:  susceptible
erythromycin: susceptible
trimethoprim/sulfamethoxazole: susceptible
vancoumycin: susceptible
What should the technologist do:

answer

the cefazolin result should be changed to resistant since the oxacillin result is resistant
Oxicillin resistant staphylococci are resistant to all beta lactam agents, beta lactam/beta lactamase inhibitor commbinatons and carbapenams. results for these antibiotics should be reorted as resistant or should not be reported

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To quality control the autoclave, a vial of bacillus stearothermophilus is autoclaved and should then be:

answer

incubated at 56*

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In a quality control procedure on a new batch of Mueller-Hinton plates using a stock culture of Staphylococcus areus, all the disk zone sizes are too small. The most likely reason for this is that the:

answer

bacterial suspension was not diluted to the proper concentration.

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Which of the following combinations of organisms would be appropriate as controls to test the functions listed?

answer

indole -negative Escherichia coli and proteus mirabilis

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A urine gram stain shows gram positive cocci in clusters. The organism tested catalase positive. To speciate this organism from culture, the technician should perform a coagulase test and a:

answer

novobiocin susceptibility

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The gram stain from a blood culture shows gram positive cocci in chains, No growth occurs on blood agar plates incubated both aerobically and anaerobically. Additional testing should be done to detect the presence of:

answer

Abiotrophia defectica
Nutritionally deficient streptococcus such as Abiotrophia defectica do not grow on sheep blood agar without the addition of cysteine or proximity to S. aureus

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Viridans streptococci can be differentiated from streptococcus pneumoniae by:

answer

bile soluability

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A reliable test for distinguishing Staphylococcus areues from other staphylococcus is:

answer

coagulase

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The optochin (ethylhydrocupreine hydrochloride) disk is used for the identificaton of:

answer

Streptococcus pneumoniae
optochin susceptibility is used to differentiat S. pneumoniae, which are susceptible , from other alpha hemolytic streptococci which are resistant

question

In the optochin susceptibility test, if there is a zone of inhibition of 19-30 mm surrounding the disk following an overnight incubation ay 37*C , the colony most likely consist of :

answer

pneumococcus
(Strep pneumococcus is susceptible, other alpha hemolytic strep are resistant)

question

Which 2 diseases are usually preceded by infection with beta hemoltic streptococci?

answer

glomerulonephritis, rheumatic fever.

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The enterotoxin produced by certian strains of hemolytic, coagulase positive Staphylococcus aureus :

answer

causes one type of bacterial food poisioning

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A gamma hemolytic Streptococcus that blackens bile esculin agar but does not grow in 6.5% NaCl broth is most likely:

answer

group D Streptococcus

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Gram stain examination from a blood culture bottle shows dark blue, spherical organisms in clusters. Growth on sheep blood agar shows small, round, pale yellow colonies. Further test should include:

answer

catalase production and coagulase test

question

Gram positive cocci in chains are seen on a gram stain from a blood culture. The organism grows as a beta hemolytic colony. Further test that could be performed include:

answer

bile esculin, PYR, bacitracin, and hippurate

bile esculin, PYR, bacitracin and hippurate are biochemical test used in the presumptive or definitive identification of beta-hemolytic streptococci such as S. pyogenes, S agalactiae and Enterococcus

question

Nutritionally deficient streptocci are:

answer

in the genera Granulicatella and Abiotrophia

question

After 21 hours a blood culture from a newborn grows catalase-negative, gram positive cocci, The bacterial colonies are small, translucient and beta-hemolytic on a blood agar plate. Biochemical test results of a pure culture are:
Bacitracin: resistant
CAMP reaction positive
bile esculin: not hydrolyzed
6.5% NaCl: no growth
Assuming that all controls react properly and reactions are verified , the next step would be to:

answer

preform a streptococcus group typing.
this describes Strep agalactiae. This can be confirmed by streptococcus antigen typing.

question

A beta hemolytic streptococcus that has been isolated from an ear culture grows up to the edge of a 0.04 unit bacitracin disk. Which of the following test would help to determine if the organism is enterococcus.

answer

growth in 6.5% NCl broth.

Enterococcus has the ability to grow in the presence of high salt concentrations such as 6.5% NaCl broth

question

The organism most commonly associated with neonatal purulent meningitis is:

answer

group B streptococccus

question

An important cause of acute exudative pharyngitus is:

answer

Streptococcus pyogenes

question

Of the following bacteria, the most frequent cause of prosthetic heart valve infections occuring within 2-3 months after surgery is:

answer

streptococcus epidermidis

question

Which of the 2 different antimicrobial agents listed below are commonly used and may result in synergistic action in the treatment of endocarditis caused by Enterococcus faecalis

answer

a penicillin derivative and an aminoglycoside

question

A catherized urine is inoculated onto blood and MacConkey agar using a 0.01 mL loopi. after 48 hours, 68 colonies of a small translucent nonhemolytic organism grew on blood agar but not MacConkey. Testing reveals small gram-positive, catalase negative cocci. The perliminary report and follow up testing would be:

answer

growth of 6,800 colonies/mL of a streptococcus species, esculin hydrolysis and NaCl growth test to follow

question

Children who have infections with Beta -hemolytic streptococci can develop:

answer

acute glomerulonephritis

question

A Gram positive coccus isolated from a blood culture has the following characteristics:
optochin susceptibility:                    negative
bacitracin 0.04 units suscepibility:   negative
bile esculin hydrolysis                      negative
hippurate hydrolysis:                        positive
catalase:                                            negative
The organism is most likely:

answer

Streptococcus agalactiae
Streptococcus agalactiae is catalase and bile esculin hydrolysis negetive and bacitracin and optochin resistant and hydrolyses hippurate

question

A beta-hemolytic Streptococcus that is bacitracin resistant and camp positive is

answer

group B strep

question

Group B, beta-hemolytic streptococci may be distinguished from other hemolytic streptococci by which of the following procedures?

answer

latex antigen typing

question

It is important to differentiate between Enterococcus and group D streptococcus because:

answer

Enterococcus often show more antibiotic resistance than group D streptococcus

question

Streptococcus pneumoniae can be differentiated beat from the viridans group by

answer

bile solubility

question

Characteristically enterococci are:

answer

relatively resistant to penicillin

question

A beta hemolytic, catalase positive, gram positive coccus is coagulase negative by the slide coagulase test. Which of the following is the most appropriate action in identification of this organism?

answer

do a tube coagulase test to confirm the slide test

question

Which of the following would best differentiate Streptococcus agalactiae fromStreptococcus pyogenes?

answer

hydrolysis of sodium hippurate

question

The most critical distinction between Staphylococcus aureus and other Staphylococcus is:

answer

coagulase production

question

Which of the folllowing organisms to date is considered universally susceptible to pencillin?

answer

Streptococcus pyogenes

question

A beta hemolytic gram=positive coccus was isolated from the cerebrospinal fluid of a two day old infant with signs of meningitis. The isolate grew on sheep blood agar under aerobic conditions and was resistant to a bacitracin disc Which of the following should be performed for the identification of the organism?.

answer

latex antigen typing
The most likley organism is Streptococcus agalactiae. Polysacchride antigen typing will confirm the identificaton the identification of S. agalactiae and differentiate it from other beta-hemolytic streptococci

question

How many hours after eating contaminated food do initial symptoms of staphyloccol food poisioning typically occur

answer

2-6 hours

question

During the past month, Staphylococcus epidermidis has been isolated from blood cultures at 2-3 times the rate from the previous year. The most logical explanation for the increase in these isolates is that:

answer

there has been a break in proper skin preperation before drawing blood for culture

question

An outbreak of Staphylococcus aureus has occured in a hospital nursery. In order to estabilish the epidemiological source of the outbreak, the most commonly used typing method is:

answer

serological typing

question

A light yellow colony from a skin leision grew aerobically and tested as catalase-negative. The organism stained a gram-positive cocci in clusters. The organism was modified oxidase positive., bacitracin (0.04U) susceptible and resistant to lysostaphin. What is the identification of this organism?

answer

Micrococcus luteus

question

An isolate of unknown beta-hemolytic streptococcus is streaked perpendicular to a streak of beta-lysin-producing Staphylococcus aureus. After incubation a zone of arrowhead hemolysis is noted at the interface of the two streaks.What is the name of the test and the persumptive identification of the unknown Streptococcus :

answer

CAMP test
S. agalactiae

question

Which of the following may be used a a positive quality control organism for the bile esculin test.

answer

Enterococcus faecalis

question

Infection of the urinary tract is most frequently associated with:

answer

Escheria coli

question

MacConkey media for screening suspected cases of hemoragic E. coli O157:H7 must contain:

answer

sorbital

question

Members of the family enterobacteriaceae share which of the following characteristics:

answer

reduce nitrate to nitrite

question

Which of the following genera is among the least biochemically reactive members of the Enterobacteriaceae ?

answer

Shigella

question

Which one of the following gram negative bacilli ferments glucose?

answer

Yersinia enterocolitica

question

A sputum culture from an alcoholic seen in the ER grows gray, mucoid, stringy colonies on sheep blood agar. The isolates grows redily on MacConkey agar and forms mucoid, dark pink colonies. The colonies yield the following test results:
ONPG:        +
indole         -
Glucose        +
oxidase          -
citrate            +
VP                 +
The organism is most likely

answer

Klebsiella Pneumonaie
--++

question

An organism was inoculated to a TSI tube and gave the following reactions:

alkaline slant/acid butt H₂S, gas produced

answer

Salmonella typhimurium

question

An isolate from a stool culture gives the following growth characteristics and biochemical reactions:
MacConkey agar: colorless colonies
Hektoen agar: yellow-orange colonies
TSI; acid slant/ acid butt, no gas, no H₂S
urea: positive

answer

Yersinia enterocolitica

question

A TSI tube inoculated with an organism gave the following reactions:
alkaline slant/ acid butt no H₂S, no gas produced

answer

Shigella dyentreriae

question

An organism gave the following reactions:
TSI:    acid slant/ acid butt, no H₂S, gas produced
indole:      positive
motility:      positive
citrate:    negative
lysine decarboxylase:    positive
Urea:      negative
VP: negative
This organism most likely is

answer

Escherecia coli
++--

question

Which of the following organisms can grow in the small bowel and cause diarrhea in children, travelers diarrhea, or severe cholera- like syndrome through the production of enterotoxins

answer

Escherichia coli

question

One of the enterotoxins produced by the enterotoxigenic Escherichea coli in travelers diarrhea is similar to a toxin produced by

answer

Vibrio cholerae

question

Shigella species characteristically are:

answer

nonmotile

question

A gram negative bacillus has been isolated from feces, and the confirmed biochemical reactions fit those of Shigella. The organism does not agglutinate in shigella antisera. What should be done next?

answer

boil the organism and retest the antisera

question

Biochemical reactions of an organism are consistant with Shigella. A suspension is tested in: antiserum without resulting agglutination: However, after 15 minutes of boiling , agglutination occurs in group D antisera. The Shegilla species is:

answer

sonnei

question

>100,000 CFU/mL of a gram- negative bacilli were isolated on MacConkey from a urine specimen. Biochemical results are as follows:
glucose:                   acid, gas produced
indole:                       negative
urea:                          positive
TDA:                          positive
H₂S:                           positive
The organism is most likely:

answer

Proteus mirablis

question

A urine culture had the following culture results:
sheep blood             swarming
Columbia CNA :    no growth
MacConkey:         1. >100,000CFU/mL nonlactose-fermenter
                              2.> 100,000 CFU/mL nonlactose-fermenter with red pigment
The isolates from MacConkey agar had the following biochemical reactions.
TEST              isolate1                 isolate2
TSI                alk/acid                 alk/acid
urea               positive                  negative
TDA              positive                 negative
H₂S              positive                 negative
The organism is most likely

answer

Proteus vulgaris and serratia marcescens

question

An 8 year old girl was admitted to the hospital with a three day history of fever, abdominal pain, diarrhea, and vomiting. A stool culture grew many lactose- negative colonies that yiealded the following test results.
oxidase:      negative
TSI              acid slant/acid butt
indole:         negative
urease:        positive
ornithine decarboxylase:         positive
H₂S:           negative
motility at 25*C                      positive

answer

Yersinia enterocolitica

question

Which of the following sets of test best differentiates Salmonella and Citrobacter species?

answer

(citrobacter+)KCN, malonate, beta-galactosidase,
(salmonella+)lysine decarboxylase

question

A fecal specimen, inoculated to Xylose lysine deoxycholate (XLD) and Hektoen enteric (HE) produced colonies with black centers. Additional testing results are as follows
TEST      | result             serological test       result
glucose     positive           polyvalent           no agglutination
H₂S         positive            Group A             no agglutination
Lysine decarboxylase po Group B           no agglutination
Urea          negative           Group C             no agglutination
ONPG      negative            Group D            no agglutination
Indole       positive             Group V          no agglutination
The most probable identification is:

answer

Edwardsella tarda

question

A 10 year old boy was admitted to the emergency room with lower right quadrant pain and tenderness. The following laboratory resuts were obtained:
                    Paitent value         normal range
% segs               75%                       16-60%
WBC count        200                       13
The admitting diagnosis was appendicitis. During surgery the appendix appeared normal; an enlarged node was removed and cultured. Small gram negative bacilli were isolated from the room temperature plate. The organism most likely is:

answer

Yersinia entercolitica

question

A 25 year old man who has had recently worked as a steward on a transatlantic grain ship presented to the emergency room with high fever, diarrhea and prostration. Axillary lymph nodes were hemorragic and enlarged. A Wayson strain of aspirate showed bacilli that were bipolor resembling saftey pins. The most likely identification of this organism is:

answer

Yersinia pestis

question

Biochemical reactions of an organism are consistant with Salmonella . A suspension is tested in polyvalent antiserum A through G and Vi antiserum. There is agglutination in the Vi antiserum only. What should be done next?

answer

Repeat the biochemical identification of the organism.

question

A clean catch urine sample from a nursing home patient is cultured using a .001 mL loop. It grows 67 colonies of a lactose fermenter that has the following biochemical reactions:
TSI: acid/acid
Oxidase: negative
Motility: positive
Indole: negative
Citrate: positive
VP: positive
Lysine decarboxylase: negative
Orinthine decarboxylase: positive
Urea: negative
What should the microbiologist report?

answer

67,000 colonies CFU/mL Enterobacter cloace

question

Plesiomonas shgellosis is a relatively new mwmber of the family Enterobacteriaceae. What characteristic separates it from other members of the Enterobacteriaceae?

answer

it is oxidase positive

question

A 64 year old man with lymphoma has a positive blood culture at 18 hours incubation. The organism is a nonlactose fermenting gram-negative bacillis on MacConkey agar. Further testing gives the following reactions:
oxidase: negative
TSI: alk/acid (no H2S)
motility : positive
indole: positive
citrate positive (morganella is citrate neg)
orinthine decarboxylase: negative
urea: positive
PAD: positive
VP: negative
The genus is:

answer

provedencia

question

The stock cultures that needed for quality control of motility are:

answer

Klebsiella pneumoniae/Escherichia coli

question

The stock cultures that needed for quality control testing of oxidase production are:

answer

Echericheia coli and Pseudomonas aruginosa

question

The stock cultures that needed for quality control testing of deamination activity are:
(PAD)

answer

Proteus mirabilis and Echericheia coli

question

The stock cultures that needed for quality control testing of deoxyribonuclease (Dnase) production are:

answer

Serratia marcescens/Echericheia coli

question

Quality control of the spot indole test requires the use of ATCC cultures of:

answer

Echericheia coli / Enterobacter cloacae

question

An organism that exhibits the satellite phenomenon around colonies of staphylococci is:

answer

Haemophilus influenzae

question

An organism isolated from the surface of a skin burn is found to produce a diffusible green pigment on a blood agar plate. Further studies of the organism would most likely show the organsim to be:

answer

Pseudomonas aruginosa

question

A nonfermenting gram negative bacillus is isolated from a wound. The nitrate and oxidase are strongly positive. The growth on sheep blood agar has a grape like ordor. The organism is

answer

Pseudomonas aruginosa

question

A nonfermenting gram negative bacillis is isolated from an eye culture. It grows only on chocolate agar and is oxidase negative. The most likely organism is

answer

haemophillus influenza

question

A blood culture with macroscopic signs of growth is Gram stained and the technician notes small, curved gran-negative bacilli resembling gull wings. It is subcultured to blood and chocolate agar, and incubated aerobically and anaerobically. After 24 hours, no growth is apparent . The next step would be to:

answer

subculture the bottle and incubate it in microaerophilic conditions.
Campylobacter

question

The optimal incubator temperature for isolation of the Campylobacter jejuni/coli group is

answer

42*C

question

A patient with a nosocomial pneumonia has a sputum gram stain that shows many neutrophils and numerous small gram negative cocobacilli. The organism grew in 24 hours as a mucoid hemolytic colony on blood agar and a colorless colony on MacConkey agar. The organism had the following characteristics :
oxidase : negative
catalase: positive
nitrate: positive
ONPG: negative
orinthine decarboxylase: negative
lysine decarboxylase: negative

answer

Acinetobacter baumanni

question

A gastroenterologist submits a gastric biopsy from a patient with a gastric ulcer. To obtain presumptive evidence of Helicobacter pylori, a portion of the specimen should be added to which media?

answer

urea broth

question

A 4 year old boy is admitted to the hospital with suspected meningitis. He has not had most of the childhood vaccines. The suspected pathogen is:

answer

Haemophilus influenza
Heamophilus influenza was previously the most common cause of bacterial meningitis in young children. However, the Haemophilus influenza type B vaccine has been in use for several years, resulting in a low incidence of H influenza causing meningitus. This patient has not had most childhood vaccinations, so he susceptible to H influenza.

question

Acinetobacter Iwoffii differs from neisseria gonorrhoeae in that the former:

answer

Will grow on MacConkey and EMB media
Both organisms are gram negative. Neisseria gonorrhoea is fastidious and does not grow on MacConkey or EMB agar, but Acinetobacter is oxidase negative.

question

A 4 year old boy is admitted with symptoms of meningitis, and a gram stain of the cerebrospinal fluid reveals small, pleomorphic, gram-negative cocobacilli. After 24 hours incubation at 35*C, small, moist, gray colonies, which are oxidase negative, are found on the chocolate agar plate only. Which of the following biochemical data would be consistant with this isolate?

answer

X factor no growth
V factor no growth
X and V growth
Haemophilus influenza needs X and V both.
chocolate has X and V

question

A gram stain of a touch prep from a gastric biopsy shows gram-negative bacilli that are slender and curved. The most likely pathogen is:

answer

Helicobacter pylori

question

A cerebrospinal fluid has been inoculated onto sheep blood and chocolate agar plates and into a tube of trytocase soy broth. All media were incubated in an atmosphere of 5% CO₂. Which of the following organisms would usually be isolated by this procedure?

answer

Haemophilus influenza

question

If present, a characteristic that is helpful in separating Pseudomonas from other members of the Pseudomonas family is:

answer

growth at 42*C
Pseudomonas aruginosa grows at 42, but this temperature is inhibitory for other Pseudomonas.

question

A Camplobacter species isolated from a stool culture gives the following biochemical reactions
nalidixic acid: susceptible
cephalothin: resistant
hippurate hydrolysis: positive
Oxidase: positive
Catalase: positive

answer

Campylobacter jejuni
Campylobacter jejuni and C. Coli are closely related and both are pathogens. The test differentiates the two is hippurate hydrolysis.

question

Which one of the following results is typical of Campylobacter jejuni?

answer

Optimal growth at 42*C
Campylobacter jejuni will grow at 37 but prefers 42. It is oxidase and catalase positive and motile.

question

Optimum growth of Campylobacter jejuni is obtained on suitable media incubated at 42*C in an atmosphere containing

answer

6% O₂, 10-15% CO₂, 85-95% nitrogen?Campylobacter is microaeroplilic, and requires a decreased oxygen and increased carbon dioxide atmosphere for growth.

question

The porphyrin test was devised to detect strains of Haemophilus capable of:

answer

synthesis of hemin
The porphyrin test is an alternative method for detecting heme-producing species of Haemophilus. It detects whether or not the organism converts the substrate delta amino levulinic acid into porphyrins or porphobilinogen, which are intermediates in synthesis of factor X.

question

Haemophilus influenza is most likely considered normal indigenous flora in the:

answer

oropharynx
Upper respiratory tract.

question

Haemophilus influenza becomes resistant to ampicillin when the organism produces a:

answer

beta-lactimase enzyme
the beta-lactamase enzyme produced by Haemophilus influenza inactivates the antibiotics that have a beta-lactam ring in their structure, such as penicillins and cephalosporins.

question

An isolate on chocolate agar from a patient with epiglotitis was suggestive of Haemophilus species. Additional testing showed that the isolate required NAD for growth and was nonhemolytic. The organism is most likely haemophilus:

answer

parainfluinza Haemophilus parainfluenza requires NAD for growth but not Hemin. This distinguishes it from H. Influenzae. H. Haemolyticus is hemolytic, and H. Ducreyi does not cause epiglotitts.

question

Which of the following specimens is considered to be the most sensitive for the recovery of Brucella in cases of chronic infection?

answer

bone marrow Bone marrow is considered the most sensitive specimen for the recovery of brucella

question

A genus that is found in soil and water and causes infection in immunocompromised patients has the following characteristics:
sheep blood agar: violet pigment
MacConkey agar: growth
42*C incubation: growth
Oxidase: Postive
OF glucose: fermenter
indole: negayive
The Genus is:

answer

Chromobacterium
the purple color on blood gives this away

question

Which of the following results is typical of Campylobacter fetus subspecies fetus?

answer

Growth at 37*C

question

Multiple blood cultures from a patient with endocarditis grew a facultative anaerobic, pleomorphic gram- negative bacilli with the following characteristics:
hemolysis; negative
MacConkey agar: no growth
Sheep blood agar: growth in 5%-10% CO2
chocolate agar: : growth in 5%-10% CO2
catalase : negative
V factor: not required
X facter: not required
oxidase: negative
Nitrite: positive
Indole: negative
The most likely identification is:

answer

Haemophilus aphrophilus

question

A gram negative bacillus with bipolor staining was isolated from a wound infection caused by a bite from a pet cat. The following characteristics reactions were seen:
oxidase: positive
glucose OF: fermentive
catalase: positive
motility: negative
MacConkey agar: no growth
Which of the following is the most likely organism?

answer

Pasturella multicida

question

A culture from an infected dog bite on a small boys finger yielded a small, gram negative cocobacillus that was smooth, raised and beta-hemolytic on blood agar. The isolate grew on MacConkey agar, forming colorless colonies. The organism was motile, catalase positive , oxidase positive, reduced nitrate and was urease positive within 4 hours. No carbohydrates were fermented. The most likely identification is;

answer

Bordetella bronchiseptica

pasturella multicida does not grow on MacConkey,and is not motile

question

While swimming in a lake near his home, a young boy cut his foot, and an infection developed. The culture grew a nonfastideous gram-negative , oxidase positive , beta-haemolytic, motile bacilli that produced deoxyribinose. The most likely identification is:

answer

Aeromonas hydrophilia
Wounds contaminated with water

question

An aerobic, gram negative cocobacillus was isolated on Bordet-Gengou agar from a nasopharyngeal swab 48 hours after culture from a 6 month-old infant with suspected pertusis. The organism exhibited the following characteristics:
MacConkey agar: no growth
Urea: negative at 4 houes, positive at 24 hours
Oxidase negative
catalase: positive
The most probable identification of this isolate is:

answer

Bordetella pertussis
The oxidase and urea reactions differentiate Bordetella pertussis aand B parapertussis.
B pertussis is oxidase positive and urea positive

question

Which of the following characteristics best differentiates Bordetella bronchiseptica from Alcaligenes species?

answer

rapid hydrolysis of urea

bordeletella bronchiseptica is urease positive in 4 hours.

question

Serum samples collected from a patient with pneumonia demonstrate a rising antibody titer to Legionella. A broncheoalveolar (BAL) specimen from this patient has a positive antigen test for Legionella but no organisms were recovered on buffered charcoal yeast extract medium after 2 days of incubation. The best explanation is that the :

answer

culture was not incubated long enough

Media for isolation of Legionella should be incubated 235-37*c FOR AT LEAST 7 DAYS.

question

Which characteristic best differentiates Acinetobacter species from Moraxella species?

answer

Production of indophenol oxidase.
Both Acinetobacter and Moraxella display resistance to penicillin, and some species grow on MacConkey agar. Acinetobacter are oxidase negative, and Moraxella are oxidase positive

question

An organism has been identified as a member of the fluorescent group of pseudomonas, Which of the following sets of test should be used to determine the species of the organism?

answer

Growth at 42*C, pyocyanin, gelatinase production.
gelatinase production separates Pseudomonas putida (negative) from Pseudomonas Fluorescence (positive)

question

Appropriate culture requirements for a patient suspected of having tularemia include:

answer

A media with cysteine , such as buffered charcoal yeast extract agar

question

A child was bitten on the arm by her sibling and the resulting wound grew a slender gram-negative bacilli that has the following characteristics:
growth on SBA: colonies that pit the agar
colonies odor: like bleach
Catalase: negative
oxidase: positive
TSI: no growth
The identification of this organismis:

answer

Eikenella corrodens
Pitting the agar and smell of bleach

question

Characteristics of the genus Capnophagia include:

answer

colonies are large and spreading after 2 days.

Capnocytophagia requires increased CO2 , fermenta glucose, sucrose, and lactose, and is a gram negative bacillus. Capnopcytophagia produces characteristic spreading colonies.

question

A laboratory aid recieves a bronchoscopy sample with the request for culture of Legionella. The assistant she asks a microbiologist for direaction on plating protocol. The correct response from the microbiologist is:

answer

Culture on buffered charcoal yeast extract agar with antibiotics

question

A community hospital microbiology laboratory is processing significant numbers of stool cultures because of an outbreak of diarrhea following heavy rains and flooding in the country. A media that should be incorperated in the plating protocol is:

answer

Thiosulfate citrate bile salts sucrose for vibrio species

question

A college student attended a beach party where raw oysters and other shellfish were consumed. The next day, he had symptoms of septicemia. The blood cultures grew gram negative bacilli with the following characteristics:
oxidase: positive
MacConkey agar: pink colonies
O/129 (ug): susceptible
The most likely organism is:

answer

Vibrio vulnificans
vulnificans is the only vibrio that ferments Lactose

question

Differentiating test that will separate Burkholderia from Stenotrophomonas inclue:

answer

oxidase
Stenotrophomonas is oxidase negative while most other nonfermenters are ocidase positive

question

A 17 year old female with cystic fibrosis is diagnosed with pneumonia. A sputum sample grew gram negative bacilli with yellow, smooth colonies that have the following biochemical reactions:
oxidase: positive
TSI: alk/alk
glucose: oxidized
fluorescence: negative
Lysine decarboxylase positive
The most likely organism is:

answer

Burkholderia cepatia
Berholderia cepatia is associated with respirtory infections in cyctic fibrosis patients, and the biochemicals are typical for this organism.

question

Characteristic of the HACEK group of bacteria include:

answer

requirement of 5%-10% CO2 for growth.
The HACEK group of organisms are gram negative bacilli that require increased CO2 for growth. They are commonly associated with endocarditis, and include Haemophilus species (especially H.Aphrophilus), Actinobacillus actinomycetmcomitans, Cardiobacterium hominis, Eikenella corrodens and Kingella species.

question

The Laboratory recieves a blood culture from a veterinarian who has been ill for many weeks with fevers in the afternoon and evenings, arthritus, and fatigue. The blood culture is positive after 5 days , and the organism has the following characteristics:
Gram stain: small gram negative cocobacilli
sheep blood agar: growth after 48 hours with small, smooth, raised colonies
What should the microbiologist do next:

answer

Take extra saftey precautions for brucella

question

The primary isolation of Neisseria gonorrhoeae requires:

answer

carbon dioxide

question

Assuming the agent isolated from a patients spinal fluid produces a positive oxidase test, the most likely diagnosis is:

answer

meningococcal meningitis

question

The following results were obtained from a culture of unknown origin:
Gram stain: gram negative diplococci
indophenol oxidase : positive
glucose: poositive
Maltose: negative
Sucrose: negative
The most likely source of the specimen would be the:

answer

Genitourinary tract

question

A ureatheral swab obtained from a man with a uretheral exudate was plated directly on chocolate agar and modified Thayer Martin agar, and a gram stain was made . Thr gram stain showed gram negative diplococi. The culture plates were incubated at 35*C, but had no growth at 48 hours. The most likely failure for organism growth is that the:

answer

Organism rerqiures CO₂ for growth.

question

A gram stain performed on a sputum specimen revealed gram -negative dipilococci within PMNs. Oxidase testing is positive and carbohydrate degredation test are inert. The organism is:

answer

Moraxella catarrhalis
(all other niesseria ferment carbohydrates)

question

Coagglutination is associated with:

answer

Neisseria gonorrhea
One of the less commonly used methods for identification of neisseria gonorrhoeae grown in culture is coagglutination

question

Clinical resistance to penicillin coorelates most frequently with beta-lactamase production in:

answer

Niesseria gonorrhea

question

All of the species of the genus Neisseria have the enzyme to oxidize:

answer

tetramethyl-phenylenediamine
(they are all oxidase positive)

question

The diagnosis of Neisseria gonorrhoeae in females is best made from:

answer

An endocervical culture

question

A vaginal smear is submitted for a gram stain for niesseria gonorrhoea. The technologist finds the following results on the gram stain:
many white blood cells
few epithelial cells
many gram postitve cocci
few gram negative diplococci
few gram positive cocci in chains
The technologist should :

answer

Not read or report a gram stain on a vaginal specimen

question

Which of the following is the most reliable test to differentiate Neisseria lactamica from Neisseria meningidis?

answer

lactose degradation

Neisseria lactamica ferments lactose, Neiserria meningidis does not.

question

Definitive identification of Neisseria gonorrhea is made with the:

answer

Hydrolysis of carbohydrates

question

A gram-negative diplococcus that grows on modified Thayer Martin medium can be further confirmed as Neisseria gonorrhoea if it is:

answer

oxidase positive and glucose positive, maltose negative

question

An organism previously thought to be non-pathogenic, Moraxella catarrhalis, is now known to be associated with oppertunistic respiratory infection and nosicomial transmission. Characteristic identification criteria include:

answer

Carbohydrate negative
(asaccharolytic)

question

An autopsy performed on an 8 year old child revealed Waterhouse-Freidrickson syndrome. Blood and throat cultures taken prior to death were positive for which organism?

answer

Neisseria meningitidis

question

An aspirated specimen of purulent material was obtained from a brain abcess. After 24 hours incubation , pinpoint colonies grew on sheep blood and small yellowish colonies grew on chocolate. Gram stain of the organism showed gram negative cocci. Results of carbohydrate degradation studies were as follows:
glucose: acid
maltose: acid
sucrose: acid
lactose: negative
Additioonal testing revealed that the organism was oxidase positive and beta-galactosidase negative. The organism is most likely Neisseria:

answer

sicca

the only one listed that ferments glucose, maltose, and sucrose

question

****************GPB**********************
A gram stain of organisms on Loffler agar showed pleomorphic gram-positive bacilli.The organism should be subcultured to:

answer

potassium tellurite

(corynebacterium diptheria)

question

Which organism commonly causes food poisioning by consumption of foods containing excessive population of organisms or preformed enterotoxin?

answer

Bacillus cereus

question

An organism recovered from a sputum has the following characteristics:
Culture: growth at 7 days on lowenstein-jensen agar, incubated under aerobic conditions with CO2 at 35*C.
Gram-stain: delicate branching gram-positive bacilli
acid-fast staining: Branching, filimentous , "partially" acid fast bacterium
These results are consistant with which of the following genera?

answer

Nocardia

question

The best procedure to differentiate Listeria monocytogenes from Corynebacterium species is:

answer

motility at 25*C

question

Establishing the pathogenicity of a microorganism isolated from a childs throat and identified as Corynebacterium diptheria would depend upon:

answer

a positive toxigenicity test In order to determine if an isolate of Corynebacterium diptheria produces toxin,
testing for the presence of diptheria toxin must be performed using methods such as the Elek test or PCR

question

Which features distinguishes Erysipelothrix from other clinically significant non-sporeforming, gram positive , facultatively anaerobic bacilli?

answer

H₂S production
the only one

question

Listeria can be confused with some streptococci because of its haemolyisis and because it is:

answer

esculin positive

Ummm...its a GPB???

question

Fluid from a cutaneous black lesion was submitted for a routine bacterial culure. After 18 hours of incubation at 35*C there was no growth on MacConkey agar, but 3+ growth on sheep blood agar. The colonies were non-hemolytic, nonmotile, 4-5 mm in diameter and off white with a ground glass appearance. Each colony had an irregular edge with comma shaped outgrowths that stood up like"beaten egg whites"when gently lifted with an inpculating needle. A gram stain of a typical colony showed large, gram-positive retangular bacilli, The organism is most likely:

answer

Bacillis antracis.

NON-HEMOLYTIC and NON-MOTILE

question

A branching gram positive. partially acid-fast organism is isolated from a brochhial washing on a 63 year old woman recieving chemotherapy. The organism does not hydrolyse casein, tyrosine or xanthine. The most likely identification is:

answer

Norcardia asteriodes.

question

*****************ANAEROBES*****************
The characteristic that is most commonly associated with the persence of strict anaerobic bacteria and can be taken as presumtive evidence of their presence in a clinical specimen is the:

answer

presence of a foul, putrid odor from tissue specimens and cultures

question

Gram stain of a thigh wound showed many gram-positive spore forming bacilli.The specimen was placed on brain heart infusion blood agar and incubated aerobically at 35*C for 3 days.At the end of that time , the plates showed no growth. The most likely explanation is that some of the specimen should have been incubated:

answer

anaerobically

question

An aspirate of a deep wound was plated on blood agar aerobically and anaerobically. At 24 hours there was growth on the anaerobic plate only. The next step in the evaluation of this culture is to:

answer

begin organism identification

question

Anaerobic infections differ from aerobic infections in which of the following?

answer

they are usually Polymicrobic

question

The following growth results were observed on media inoculated with a foot abcess aspirate and inoculated in 3%-5% CO2.
SBA: 2+ large gray colonies
PEA: no growth
chocolate: 3+ large gray colonies
MacConkey: 3+ lactose fermenters
trytocase soy broth: gram negative bacilli and gram-positive bacilli
Biochemicals were set up on the colonies from the MacConkey agar plate. What should the microbiologist do next?

answer

Subculture TSB to SBA aerobic and SBA anaerobic.

question

Which of the following pairs of organisms usually grow on kanamycin, vancoumycin, laked blood agar?

answer

Bacteroides and prevotella

question

Acceptible specimens for culture of anaerobic bacteria that cause disease include:

answer

abscesses

question

Proprionibacterium acnes is most often associated with:

answer

blood culture contamination

question

The etiologic agent of botulism is

answer

an endotoxin producer

question

A strict anaerobe that produces terminal spores is

answer

clostridium tetani

question

An anaerobic spore forming , nonmotile, gram positive, bacillus isolated from a foot wound is most likely:

answer

Clostridium perfringens

question

The lab has been using a latex agglutination assay to detect Clostridium difficile in stools, which identifies a non toxin cell wall antigen. The lab is considering adoption of an EIA method that detects Clostridium difficile toxin A. Which of the following would provide the best compairison?

answer

latex agglutionation vs culture on cycloserine cefoxitin egg-fructose agar
(the gold standard for toxin detection)

question

The reverse CAMP test , lecthinase production , double zone of hemolysis, and Gram-stain morphology are all useful criteria in the identification of:

answer

Clostridium perfringens

question

Which one of the following anaerobes is inhibited by sodium polyanethiol sulfate (SPS)?

answer

peptostreptococcus anaerobius

question

At the persent time Clostridium difficile toxin can be detected by:

answer

EIA

question

An anaerobic gram-positive bacili with subterminal spores was isolated from a peritoneal abscess. The most likely identification of this organism is:

answer

Clostridium septicum

question

The most meaningful laboratory procedure in confirming the diagnosis of clinical botulism is:

answer

demonstration of toxin in the patients serum

question

A stool sample is sent to the laboratory for culture to rule out Clostridium difficile. What media should the microbiologist use and what is the appearance of the organism on this media?

answer

CCFA yellow, ground glass colonies.

question

A gram stain of drainage from a pulmonary sinus tract shows many WBCs and 3+ branching gram positive bacilli. Colonies grow on anaerobic media after 3 days incubation. They are yellow tan and have a molor tooth appearance. The most likely genus is:

answer

Actinomyces

question

Which organism is the most common anaerobic isolated from infectious processes of soft tissue and anaerobic bacteremia?

answer

Bacteroides fragilis

question

Which of the following genera include anaerobic gram negative non-sporeforming bacilli?

answer

Bacteroides

question

An organism from a peritoneal abscess is isolated on kanamycin-vancoumycin laked blood agar and grows black colonies on BBE agar. It is nonpigmented, catalase positive, and indole negative. The genus of this organism is:

answer

Bacteriodes

question

Which of the following sets of organisms may exhibit a brick red flourescnce?

answer

Veilonella parvula and Prevotella melaninogenica

question

Which of the following sets of organisms may exhibit brick red flourescesce ?

answer

Vionella paruva and Prevotella melaninogenia

question

A 1-2 mm translucent, nonpigmented colony, isolated from an anaerobic culture of a lung abscess after 72 hours, was found to flouresce brick-red inder ultra-violet light. A gram stain of the organism revealed a cocobacillus that had the following characteristics:
growth in bile: inhibited
vancoumycin: resistant
kanamycin: resistant
colistin: susceptible
esculin hydrolysis: negative
indole: negative
The identification of this isolate is:

answer

Provotella melaninogenica

question

A thin gram-negativebacillus with tapered ends isolated from an empyema specimen grew only on anaerobic sheep blood agar . It was found to be indole positive, lipase negative, and was inhibited by 20% bile. The most probable identification of this isolate would be?

answer

Fusobacterium nucleatum

question

Which of the following anaerobes would be negative for indole?

answer

Bacteriodes fragilis

question

The presence of 20% bile in agar will allow growth of:

answer

Bacteriodes ovatus

question

A control strain of Clostridium should be used in an anaerobic jar to assure:

answer

That ananaerobic enviroment is achieved.

question

Which of the following organisms could be used as the positive quality control test for lacthinase on egg yolk agar?

answer

Closteridium perfringens

question

*****************FUNGI*******************
The major features by which molds are routinely identified are:

answer

Macroscopic characteristice and microscopic morphology

question

A sputum specimen from a patient with a known Klebsiella pneumoniae infection is recieved in the laboratory for a fungus culture. The proper procedure for handling this specimen is to:

answer

include media that have cyclohexamide and chloamphenocol added to inhibit bacteria

question

Many fungal infections are transmitted to man via inhalation of infectious structures. Which of the following is usually contracted in this manner?

answer

Histoplasma capsulatum

question

A smear of skin tissue reveals fluorescent septate hyphae. The smear was prepared using:

answer

calcaflour white

question

Anti-fungal susceptbility test for yeast are:

answer

more useful in identifying resistant strains

question

In perparing an india ink slide, the technician should ensure that the :

answer

Proper amount of reagent is added.
too much india ink blocks transmission of light.

question

An organism that demonstrates budding yeast cells with wide capsules in an india ink preparation of spinal fluid is probably:

answer

Cryptococcus neoformans
Cryptococcus neoformens is a cause of meningitus in immunocompromised patients, and produces a polysaccharide capsule.

question

The formation of a germ tube presumptively identifies:

answer

Candida albicans
(Candida albicans produces germ tubes)

question

A HIV positive patient began to show signs of meningitus. A spinal fluid was collected and cultured for bacteria and fungus. A budding encapsulated yeast was recovered. Which organism is consistant with this information?

answer

Crytococcus neoformans

is a cause of meningitis in immunocompromised patients, and produces brown colonies (due to melanin production) on bird seed agar.

question

Staib medium (birbseed agar) is useful in the identification of which of the following?

answer

Crytococcus neoformans

question

Gram stain examination of a CSF specimen indicates the presence of yeast like organisms with gram positive granular inclusions . Which of the following techniques should be used next to assist in the identification of this organism?

answer

India ink
Cryptococcus neoformans may not stain well on Gram stain. Rapid identification is important when yeast is dected in CSF the presence of capsules seen in an indian ink preparation would be presumptive for C neoformans.

question

The one characteristic by which an unknown Cryptococcus species can be identified as a Cryptococcus neoformans is:

answer

positive phenol oxidase test.
Cryptococcus neoformans is the only clinically encountered yeast that is phenol oxidase positive.

question

A urine culture from a patient with a urinary tract infection yields a yeast with the following characteristics:
Failure to produce a germ tube
hyphae not formed on cornmeal agar
urease negative
assimilates trehalose
The most likely identification is:

answer

Candida glabrata
of the yeast listed only Candida glabrata is urease negative and does not produce a germ tube.

question

A yeast isolate from a CSF specimen produced the following results:
India ink: no encapsulated yeast cells
Cryptococcal antigen: negative
Urea: negative
Germ tube: negative What should the technologist do next?

answer

carbohydrate assimilation

Conventional test such as carbohydrate assimilation , must be performed for definitive identification of the yeast in this CSF specimen , especially in light of the fact that the yeast is both crypticoccal antigen and germ tube negative.

question

The recovery of cryptococcus species may be compromised if the isolation media contains:

answer

Cyclohexamide

Cyclohexamide is known to inhibit the growth of some fungal pathogens, including Cryptococcus neoformens

question

A neonatal blood culture collected through a catheter grows a small yeast, Microscopically, the yeast apear round at one end , with a budlike structure on a broad base at the other end. Growth is enhanced around olive oil saturated discs, The organism isolated is:

answer

Malassezia furfur
Malsssezia furfur cause catheter-related sepsis, requires lipids for growth, and is a small yeast with a wide bud.

question

Two blood cultures are positive for yeast from a patient with an intravenous catheter. One culture grew Candida albicans, while the other grew Candida Krusie. Which medium should the technologist use to subculture the blood bottles to in order to verify that the cultures are pure?

answer

chromogenic agar

Chromogenic agar is extremely effective in determining mixed yeast populations in clinical specimens.

question

Quality control testing of CHROMEagar, Candida medium shows very weakly colored colonies after incubation at 25*C, ambient atmosphere for 48 hours . The technologist should

answer

repeat the quality control test , but incubate at 35*C
CHROMagar produces the best color development when incubated at 35-37*C

question

The morphological characteristics of a yeast grown in rabbit plasma are shown in the image :
[image]
The most likely identification of this yeast is:

answer

Candida albicans
Candida albicans produces a tubular structure with no constrictions (germ tubes) when incubated in rabbit plasma

question

The most sensitive test for the diagnosis of cryptococcal disease is:

answer

Cryptococcal antigen
Cryptococcal latex antigen test has been proven to be significantlybmore sensitive than staining methods.

question

Which of the following statements concerning the germ tube test is true?

answer

Candida albicans(positive) and candida tropicalis(negative) can be used as positive and negative controls

question

Which of the following procedures should be performed to confirm that an unknown mold is one of the pathogenic dimorphic fungi:

answer

culture conversion to yeast form

Several monomorphic molds resemble the filamentous phase of dimorphic molds, so conversion to yeast phase must be performed for identification of dimorphic molds.

question

Lab workers should always work under a biological safety hood when working with cultures of:

answer

Coccidioides immitis
The arthroconidia of Coccidiodies immitis produce alternating arthrospores.

question

Structures important in the microscopic identification of coccidiodes immitus are:

answer

irregular staining , barrel shaped arthrospores.

question

Which of the following is the most useful morphological feature in identifying the mycealial phase of histoplasma capsulatum?

answer

8-14 tuburculate macroconidia
The presence of turberculate macroconidia indicates a presumptive identification of H capsulatum. The identification must be confirmed using nucleic acid probes or exoantigen testing

question

A mold grown at 25*C exhibited delicate septate hyline hyphae and many conidiphores extending at right angles from the hyphae Oval , 2-5 um conidia were formed at the at the end of the conidiphores giving a flower like appearance. In some areas sleeves of spores could be found along the hyphea as well. A 37*C culture of this organism produced small cigar shaped yeast cells. This organism is most likely:

answer

Sporothrix shencki
[image]

question

A fungal isolate from the sputum of a patient with a pulmonary infection is suspected to be Histoplasma capsulatum . Tuberculate macroconidia were seen on the hyphae of the mold phase, which was isolated at room temperature on Sabouraud dextrose agar containing chloramphenocol and cyclohexamide (SDA-CC). A parallel set of cultures incubated at 35*C showed bacterial growth on SDA, but no growth on SDA-CC. Which of the following is the appropriate course of action?

answer

Subculture the mold phase to moist BHI blood media, incubate at 25*C
Dimorphism differentiates Sporothrix from other fungi listed.

question

Skin scrapings obtained from the edge of a crusty wrist leision were found to contain thick walled sherical yeast cells (8-15 um in diamater) that had single buds with a wide base of attachment, Microscopic examination of the room temperature isolate from this specimen would probably reveal:
[image]

answer

round or pear shaped small conidia attached to conidiphores of irregular lenghts.
(blastomyces)

question

Examination of a fungal culture form a bronchial washing reveals white, cottony areial mycelium. A tease preparation in lactophenol cotton blue shows the structure shown in the image:
[image]
The most rapid test for definitive identification is:

answer

nucleic acid probes
(coccidoides immitis)

question

Penicillum species is isolated from a bone marrow culture of a patient that travelled to southwest Asia. After 7 days in the isolate produces a red pigment that diffuses into the medium.The technologist should.

answer

transfer a colony to BHI at 35*C
penicillim marneffei
Pennicillim marneffei is a dimorphic fungi that produces a diffusible red pigment.

question

The microscopic structures that are most useful in the identification of dermatophytes are:

answer

macroconidia and microconidia
Dermatophites include 3 genera that are generally differentiated by their macroconidia formation.

question

Which of the following is most often used to prepare a slide form a plate culture of a dermatophyte for microscopic observation?

answer

lactophenol cotton blue
Lactophenol cotton blue is used as the mounting medium, since lactic acid acts as a clearing agent, phenol acts as a killing agent, glycerol prevents drying, and cotton blue gives color to the structures.

question

A specimen of hair the flouresced under a wood lamp was obtained from a child with low grade scaling lesions of the scalp. Cultures revealed a fungus with mycelium and very few macroconidia or microconidia. The fungus is most likely:

answer

Microsporum audounii
The absence of conidia differentiates Microsporum audounii from the other dermatophytes listed.

question

Which of the following is the best aid in the identification of Epidermiphyton floccosum?

answer

smooth walls clubbed shaped

question

Culture of a strand of hair that fluorsced yellow-green when examined with a woods lamp produced a slow growing , flat gray colony with a salmon pink reverse. Microscopic examination demonstrated raquet hyphae, pectinate bodies, chlamdophores, and a few abortive or bizzarre shaped macroconidia. The most likely identification of this isolate is:

answer

Microsporum audounii
[image]
Hair that flouresces yellow-green under a Woods lamp indicates the presence of a Microsporum species. The colony morphology and microscopic characteristics are consistant with M audounii.

question

On day 3 of a fungal culture , grayish cottony growth is observed that is filling the container. The most likely mold isolate is:

answer

zygomycete
Zygomycete grow rapidly and fill the dish with cotton-candy like growth

question

The appropriate specimen for the diagnosis of mucormycosis is:

answer

eschar biopsy
Mucormycosis is an agressive infection where biopsy, curettage or fine needle aspiration is essential for diagnosis.

question

Pennicillum can best be separated from aspergillus by:

answer

arrangement of conidia and conidiphores
Microscopic morphology (arrangement of the conidia on the conidiophore) is used to differentiate Penicillum from aspergillus.

question

A fungus specifically resembels penicillum species but may be differentiated because its phialides are long and tapering and bend away from the central acis. The most probable identificationis:

answer

Paecilomyces
Elongated and tapered phialides (tenpins) are characteristic of Paecilomyces.
[image]

question

[image]
An isolate from a cornea infection had the following culture results :
Sabouraud dextrose: white and cottony at 2 days , rose color at 6 days.
Slide culture: slender cycle shaped microconidia
The most likely organism is:

answer

Fusarium
Fusarium freuquently cause corneal infections and have sickle-shaped macroconidia
[image]

question

In the USA, the most common organism causing eumycotic mycetoma is:

answer

Pseudalleschereria boydii
Mycetoma, is a slow-growing bacterial or fungal infection focused in one area of the body, usually the foot. The infection is characterized by an abnormal tissue mass beneath the skin, formation of cavities within the mass, and a fluid discharge. As the infection progresses, it affects the muscles and bones; at this advanced stage, disability may result.

question

Crust from a cauliflower like leision on the hand exhibited brown spherical bodies 6-12um in diameter when examined microscopically. After 3 weeks of incubation at room temperature , a slow growing black mold grew on Saubouraud dextrose agar. Microscopic examination revealed Cladosporium, Philophora and Fonsecaea types of sporulation. The probable identification of this organism is:

answer

[image]
Fonsecaea pedrosoi
only Fonsecaea pedrosoi produces Clalosporium, Philophora and Fonsecaea types of sporulation simutaneously.

question

Pus from a draining fistula on a foot was submitted for culture. Gross examinaton of the specimen revealed the presence of a small (0.8mm in diameter). yellowish, oval graunle. Direct microscopic examination of the crushed granule showed hyphae 3-4 um in diameter and the presence of clamdospores at the periphery . After two days a cottony, white mold was seen that turned gray with gray to black reverse after a few days. When viewed microscopically, moderately large hyline septate hyphae with long or short conidiophores, each with a single pear shaped cionidium, 5-7 x 8-10um were seen. The most likely identification is:

answer

Pseudallescheria boydii
[image]

question

In processing clinical specimens and fungal isolates , laboratory workers may contact systemic fungal infections through:

answer

inhalation
Specimens from fungal culture should be processed in a biological saftey cabinet to minimize the potential for aerosol spread

question

A sputum specimen recieved at 8 am for an AFB smear reveals acid fast bacilli. An additional sputum is submitted that afternoon. This specimen was concentrated by the NALC-sodium hydroxied method and inoculated on 2 Loewnstein -Jensen slants and held for 8 weeks at 35*C in 5-10% CO2. No growth occurs. The best explanation is that:

answer

An improper specimen was submitted for culture.
Early morning sputum specimens are optimal for AFB cultures.

question

The preferred carbon source for mycobacteria is:

answer

glycerol
(mycobacteria use glycerol as a carbon source in the presence of mineral salts).

question

The first morning sputum is recieved for culture of mycobacteria. It is digested and concentrated by the N-aceytal-L-cystine alkali method. Two Lowenstein jensen slants are incubated in the dark at 35*C with 5-10% CO₂. The smears reveal acid fast bacilli, and after 7 no growth appears in the slants . The best explanation is?

answer

cultures are held for an insufficient length of time.
Many species of mycobacterium are slow growing and may take up to 12 weeks for growth.

question

A first morning sputum is recieved for Acid fast culture. The specimen is centrafuged, and the sediment is innoculated on two Lowenstein jensen slants, which are incubated at 35*C with 5-10% CO2, After 1 week the slants show abundant growth over the entire surface. Stains reveal gram-negative bacilli. To avoid this problem:

answer

decontaminate the specimen with sodium hydroxide.
Specimens contaminated by normal flora must be decontaminated prior to innoculation of media; NaOH is the most common decontaminate.

question

A first morning sputum is recieved for culture of Acid fast bacilli. It is digested and concentrated by the N-aceytal-L-cystine alkali method.Two Sabouraud dextrose slants are incubated in the dark at 35*C with 5-10% CO₂. The smears reveal acid-fast bacilli, but the slants show no growth after 8 weeks, The explanation is:

answer

Improper media was used.
Sabouraud dextrose slants are fungal media; mycobacteria media should have been inoculated.

question

In reviewing the number of mycobacterium isolates for the current year; it was noted that there were 76% fewer isolates than the previous year (115 vs 28). The technoloist in charge of the area has documented that the quality control of the media, reagents and stains has been acceptible and there has been no gross contamination of the cultres noted. The most appropriate course of action to pursue would be:

answer

Review the digestion and decontamination procedure.
The concentration of sodium hydroxyide may be too strong to decrese recovery of AFB and lack of contaminated cultures.

question

Which of the following combinations of media provides an egg base, agar base, and a selective egg or agar based media.

answer

Lowenstein jensen(egg), Middlebrook 7H11(agar), Lowenstein jensen Gruft(egg or agar)

question

Which of the following reagents should be used as a mucolic, akaline reagent for digestion and decontamination of a sputum for mycobacteria culture?

answer

N-acetly-L-cystine and NaOH

question

The function of
N-acetly-L-cystine and NaOH In the reagent for acid-fast digestion -decontamination procedure is to:

answer

liqufy the mucus
N-acetly-L-cystine (NALC) is a mucolic agent; the concentration of NALC may be increased to digest thick , mucoid specimens.

question

When staining acid fast bacilli with truant auramine-rhodamine stain, potassium permanganate is used to:

answer

quenching agent
The counter stain acts as a quenching agent and reduces the background flourescence of culture debries

question

Middlebrook 7H10 and 7H11 media must be refrigerated in the dark, and incubated in the dark as well. If these conditions are not met , the media may prove toxic for mycobacterium because:

answer

Formaldehyde may be produced
(Which is toxic to mycobacteria)

question

The method for processing specimens for mycobacterial culture contaminated with Pseudomonas is:

answer

Oxalic acid
The oxalic acid method is superior to alkali methods for processing specimens contaminated with Pseudomonas.

question

An AFB broth culture is positive for acid fast bacilli at 1 week while the agar slant shows no growth. The most likely explanation for this is:

answer

AFB grow more rapidly in liquid media

question

A bronchial washing is processed for acid-fast bacilli. Which of the following precautions should be taken in order to prevent infection of laborotory personnel?

answer

Process all specimens in a biological hood

question

Tubercle bacilli are specifically stained by:

answer

carbol fusion
Mycobacterium form stable complexes with Kinyoun carbol fusion

question

The species of mycobacteria that will give a positive niacin test is Mycobacterium:

answer

Tuberculosis
a positive niacin reaction differentiates Mycobacterium tuberculosis from M leprae, M kansasii and M fortuitum.

question

A digested and decontaminated sputun is inoculated into a Bactec 12B bottle and incubated in air at 37*C. On day 14, positive growth index is obtained, and the auramine-rhodamiine stain is positive. Broth from the initial bottle is inoculated into one-Bactec 12B bottle, and one Bactec 12B bottle with NAP. After incubation, the inoculated growth bottle shows an increase in growth index, while bottle containing NAP shows no increase. The organism cultured from the sputum is most likely Mycobacterium:

answer

Tuberculosis
Mycobacterium tuberculosis and Mycobacterium bovis cannot grow in the presence of NAP.

question

On a culture suspected to be mycobacteium tuberculosis, the most important test to preform is:

answer

niacin production
A positive niacin test differentiates Mycobacterium tuberculosis from most other mycobacteria.

question

A positive niacin test is most characteristic of Mycobacterium :

answer

tuberculosis
Growth rate, colony morphology,and niacin reduction differentiate Mycobacterium tuberculosis from other mycobacteria

question

Characteristics necessary for the definitiive identification of Mycobacterium tuberculosis are:

answer

rough, nonpigmented colony, slow growth at 37*C, niacin production-positive, nitrate production positive
tuberculosis
Growth rate, colony morphology,and niacin reduction differentiate Mycobacterium tuberculosis from other mycobacteria

question

A two week old culture of a urine specimen produced a few colonies of acid-fast bacilli, which were rough and nonpigmented. The niacin test was weakly positive and the nitrate test was positive. Which of the following is the most appropriate action when a presumptive identification has been requested as soon as possible?

answer

Wait a few days and repeat the niacin test; report presumptive Mycobacterium tuberculosis if the test is more strongly positive.

question

The disease producing capacity of Mycobacterium tuberculosis depends primarily upon:

answer

Capacity to withstand intra-cellular digestion by macrophages.
Mycobacterium can remain viable but dormant in macrophages for many years.

question

Which species of mycobacterium includes a BCG strain used for vaccination aginst tuberculosis?

answer

bovis
Mycobacterium can remain viable but dormant in macrophages for many years.

question

AFB smear positive respiratory specimens may be reliably identified as mycobacterium tuberculosis the same day the smear was read by:

answer

nucleic acid amplification test
(PCR)

Several commercial PCR tests are available that identify Mycobacterium tuberculosis from positive respiratory specimens.

question

A physician call the laboratory to verify a result of Mycobacterium tuberculosis, stating that the clinical history of the patient is not compatible with tuberculosis. On review of the patients culture , the smear was negative and the culture became positive at 5 weeks in the broth culture only. Additionally, it was determined that another patients specimen that was processed the same day was 4+ AFB on smear and the culture was positive at 10 days for Mycobacterium tuberculosis. The lab should:

answer

Perform molecular fingerprinting on both slides.if the molecular finger print is the same on both slides, the lab should review its processing procedures.

If the molecular fingerprint is the same, the smear neagtive culture sould be considered a false positive, and the laboratory should review its processing procedures

question

Which of the following is considered a primary drug for the treatment of Mycobacterium Mycobacterium tuberculosis?

answer

rifampin
The primary drugs for the treatment of Mycobacterium tuberculosis include ionizid, rifampin, pyrazinamide, and ethambutol.

question

An unusual number of Mycobacterium gordonae have been isolated. The most likely source is:

answer

Contamination by water organisms

Mycobacterium gordonae is widely distributed in soil and water., and is generally considered nonpathogenic.

question

When grown in the dark, yellow to orange pigmentation of the colonies is usually demonstrated by

answer

Mycobacterium scrofulacem
Mycobacterium scrofulacem is a scotochromogen.

question

The Mycobacterium that produces a deep yellow or orange pigment both in dark and light are:

answer

scotochromogens
Scotochromogens produce deep yellow or orange pigment when grown either light or darkness.

question

Mycobacterium that produce pigment only after exposure to light are classified as:

answer

photochromogens
Photochromogens produce nonpigmented colonies only when grown in darkness, but pigmented colonies after exposure to light.

question

In a suspected case of Hansen disease (Leprosy), a presumptive diagnosis is established by:

answer

detection of weakly acid-fast bacilli in infected tissue
Mycobacterium leprae cannot be cultured in vitro. A clinical diagmosis is made, supported by the presence of AFB in a biopsy specimen.

question

The best medium for culture of Mycobacterium tuberculosis is:

answer

Lowenstein jensen medium

Lowenstein jensen is an egg based medium used to isolate AFB. The other media are not used for the isolation of AFB

question

A 27 year old scuba diver has an abrasion on his left thigh. A culture of this wound grew an acid-fast organism at 30*C. This isolate is most likely:

answer

Mycobacterium marinum
Mycobacterium marinum causes infections as a result of trauma to the skin and exposure to contaminated fish tanks, or salt water. Its optimal growth temperature is 28-30*C

question

A non-chromogen that grows best at 42*C and is highly resistant to antibiotics is:

answer

Mycobacterium Xenopi
Mycobacterium Xenopi grows best at 42-45*C, and is not pigmented.

question

Photochromogens produce pigment when:

answer

exposed to light for 1 hour
Pigment production is controled by an oxygen-dependant, light-indicible enzyme in photochromogenic mycobacteria.

question

An acid-fast bacillis recovered from an induced sputum had the following characteristics:
pigmentation: yellow in the dark, turning a deeper yellow-orange after 2 weeks of light exposure
Nitrate reduction: negative
Tween hydrolysis: positive at 5-10 days
urease: negative
Based on this information, the organism is most likely Mycobacterium:

answer

gordonae
The characteristics given differentiate Mycobacterium gordonae from the other mycobacteria listed. M szulgai and flavescens are nitrate production positive, and M scrofulaceum is negative for Tween hydrolysis.

question

Which of the following characteristics best distinguishes Mycobacterium scrofulaceum from Mycobacterium gordonae?

answer

Tween hydrolysis
Tween hydrolysis differentiates Mycobacterium gordonae (Tween positive) from M Scrofulaceum (Tween negative)

question

Differentiation of Mycobacterium avium from Mycobacterium intracellulare can be accomplished by:

answer

DNA probe
Mycobacterium avium and M intracellular have the same biochemical pattern, but can be differentiated by the use of DNA probes.

question

Which of the following species of Mycobacterium does not usually fluoresce on a fluorochrome stain?

answer

Mycobacterium fortuitum

Rapidly growing mycobacteria such as Mycobacterium fortuitum may be <10% acid fast and may not stain with florochrome.

question

A mycobacterial isolate that causes multiple skin nodules, grows at 30* and requires hemin for growth is Mycobacterium:

answer

haemophilium
Mycobacterium hemophilium grows best at 30*C , requires hemin of ferric ammonium citrate for growth, and causes subcutaneous lesions presenting as multiple skin nodules.

question

AFB smears of a lymph node biopsy from a child are positive At the end of 8 weeks, the AFB cultures are no growth. To enhance the possibility of recovery of the causitive organism, the technologist should?

answer

incubate the cultures an additional 4 weeks.
Mycobacterium malmoense reqiures up to 12 weeks for growth.

question

The nitrate test for mycobacteria can be performed with a reagent impregnated paper strip or by use of standard reagents. In order to quality control the test properly, which of the following shaould be used for a positive control

answer

Mycobacterium tuberculosis
Mycobacterium tuberculosis is the only mycobacterium listed that is nitrate reduction positive.

question

**************Viruses and other Microorganisms**************

Virus transport medium containing penicillin, gentamycin and amphotericin is used to collect and transport specimens for virus culture because this medium:

answer

Inhibits bacterial and fungal growth

question

Which of the following indicates the presence of a viral infection in tissues smears or biopsys

answer

Cytopathic effect
intra nuclear and intracytoplasmic inclusions

question

Respiratory synctial virus is best isolated using a:

answer

nasopharyngeal aspirate

question

A urine specimen was submitted for isolation of cytomegalovirus (CMV) , The urine was inoculated into human fibroblast tissue culture tubes. After 72 hours, no cytopathic effect was observed in the culture tubes. The most appropriate course of action is to:

answer

Incubate the culture tubes for 2-3 weeks longer.
(cytomegalo virus is a slow growing herpesvirus and may take up to 3 weeks to grow in conventional viral culture)

question

The genus of virus associated with anogenital warts, cervical dysplasia and neoplasia is:

answer

papilomavirus
Human papilimavirus (HPV) infects epithelial tissues throughout the body, including skin, larynx, and anogenital tissue. Persistant infection with oncogenic types of HPV and intergration of HPV DNA into the cellular genome is a pathway leading to HPV induced neoplasia , such as cervical cancer.

question

Encephalitis is most commonly associated with which of the following viruses?

answer

herpies simplex
Herpes simplex virus is the most common cause of fatal sporadic encephalitis in the United States

question

Colds and other acute respiratory diseases are most often associated with:

answer

adenovirus

question

The Epstein-barr virus is associated with which of the following?

answer

Burkitt lymphoma
The classic clinical syndrome associated with Epstein-barr virus (EBV) infeection is infectious mononucleosis. However in immunocompromised patients, EBV is associated with posttransplant lymphoproliferative disorders, and maligncies such as Burkitt lymphoma

question

Which organism fails to grow on artificial media or in cell cultues?

answer

Treponemia pallidum,
Chlamydia trachomatis,Neisseria gonorrhoeae and herpes somplex virus can all be isolated in culture. Direct culture of Treponema pallidum on artificial media has not been acheived. Darkfield microscopy and serological techniques are used to diagnose T.pallidum infection.

question

Darkfield microscopy is be used to visualize:

answer

Treponemia pallidim
Darkfield microscopy can be performed to visualize Treponema palliidum in genital or skin lesions. Darkfield examination allows for the visualization of T pallidums typical morphology and motility.

question

A wright stain on conjunctival smear from a neonate shows granular cytoplasmic perinuclear inclusions . This is the most indicative of:

answer

Chlamydia trachomatis
The presence of typical intracytoplasmic inclusions are particularly useful in diagnosing Clamydia tracomatis inclusion conjunctivitus. Multinucleated giant cells are seen in cells infected with herpes simplex and varicella zoster virus. Cytomegalovirus produces large cells with intranuclear inclusions.

question

Iodine staining of McCoy cells monolayer culture of a cervical swab reveals a large brown intercytoplasmic inclusion. What is the most likely infecting organism

answer

Chlamydia trachomatis.
Iodine staining can be used to detect the glycogen rich cytoplasmic inclusions in Chlamydia trachomatis infected cells. These inclusions stain brown with iodine.

question

Which compound, detected by Lugol iodine, is used in the non-immunologic detection of Chlamydia trachomatis in cell culture:

answer

glycogen
Iodine staining can be used to detect the glycogen rich cytoplasmic inclusions in Chlamydia trachomatis infected cells. These inclusions stain brown with iodine.

question

Microorganisms resembling L-forms have been isolated from the blood of patients treated with antibiotics that:

answer

interfere with cell wall synthesis
Bacterial L-forms are bacteria that lose their cell wall as a result as a result of therapy with cell wall active antibiotics, such as beta-lactam antibotics. Unlike mycplasma species, which permanently lack a cell wall, the lack of a cell wall in L-forms is a result of enviromental conditions. Once beta-lactam therapy is discontinued, an L form has the capability to grow a cell wall

question

Relapsing fever in humans is caused by:

answer

Borrelia recurentis
Relapsing fever is caused by Borrelia recurentis and is transmitted by the human body louse. Relapsing fever is characterized by the acute onset of high fever lasting 3-7 days, interspersed with periods of no fever, lasting days to weeks.

question

Psittacosis is transmissable to man via contact with

answer

birds
Chlamydia psittaci, the agent of psittacisis, is transmitted to humans via inhalation of nasal secretions as well as infected fecal and feather dust.

question

Chamydial infections have been implicated in

answer

urethirtis and conjunctivitis
Chlamydia trachomatis is a well known cause of sexually transmitted infections. including urethritis and cervicitis, as well as inclusion conjunctivitis and pneumonia in neonates. It also causes trachoma and lymphogranulomas vernereum.

question

Mycoplasmas differ from bacteria in that they

answer

lack cell walls
Mycoplasma are smaller than other bacteria and lack a cell wall, instead they posess a trilaminar cell membrane. Because they lack a cell wall , they cannot be stained with gram stain.

question

A jaundiced 7 year old boy , with a history of playing in a pond in a rat infested area, has a urine specimen submitted for a direct darkfield examination, several spiral organisms are seen . Which of the following organisms would most likely be responsible for the patients condition?

answer

Leptospira interrogans
[image]
Leptospira are spiral shaped organisms with hooked ends. They are ubiquitous in water (eg lakes, ponds) and assiciated with renal infections in animals, Leptospirosis is a zoonosis, and humans are usually infected via direct or indirect contact contact with the urine of infected animals (including rats). Between 5%-10% of patients with leptospirosis have the icteric form and develop jaundice, and may develop acute renal failure.

question

A jaundiced 7 year old boy , with a history of playing in a pond in a rat infested area, has a urine specimen submitted for a direct darkfield examination, No organisms are seen in the specimen. Which medium should be inoculated in an attempt to isolate the suspected organism?

answer

Fletcher semi-solid
The clinical syndrome described is most likely the icteric form of Leptospira interrogans. The most commonly used medium for culture is Fletcher semisolid agar. Cultures are incubated in the dark for up to 6 weeks at 28-30*C and examined weekly for by darkfield microspy.

question

Which of the following is a growth requiremint for the isolation of Leptospira:

answer

medium containing 10% serum plus fatty acids
.
Leptospiria cultures are incubated in the dark for up to 6 weeks in amibent air at 28-30*C, and examined weekly by darkfield microscopy. Fletcher semisolid agar contains peptone, bee extract and rabbit serum, which create an enriched medium to support the growth of leptospires.

question

Blood cultures from a case of suspected leptospiremia should be drawn.

answer

in the first 7 -10 days of infection.

Leptospiria organisms can be readily detected by culturing blood during the first week of illness. After this time the organisms disapprar from blood agar and are excreated from the urine for up to 1 month.

question

What material should be used to prepare slides for direct smear examination for virus detection by special stains or FTA technique?

answer

epithelial cell from the base of the lesion

Since viruses are intracellular organisms, the collection of cellular material is required to be able to demonstrate virus using stains or florescent techniques. Scraping of the base of a vesicle are required to collect cellular material.

question

A 29 year old man is seen for recurrence of a purulent uretheral discharge 10 days after the succesful treatment of cultures proven gonorrhea. The most likely etiology of his urethritis is:

answer

Chlamydia trachomatis
Up to 1/3 of patients with Nessieria gonorrhoeae infection are also co-infected with Chlamydia trachomatis. Patients with identified infection with one organism are usually treated for both infections.

question

Ureaplasma urelyticum are difficult to grow in the laboratory on routine media because of their requirement for:

answer

sterols
Ureaplasma urelyticum, like other Mycoplasma, lack a cell wall and posess an extremely small genome. As a result, this organism has a limited biosynthetic capability and fastidious growth requirements. culture medium should contain serum (provides sterols), growth factors such as yeast extract and a metabolic substrate.

question

A cell culture line used for the recovery of Chlamydia trachomatis from clinical specimens is

answer

McCoy cells
McCoy cells in addition to buffalo green monkey kidney cells, are susceptible to infection with Chlamydia trachomatis, and are used routinely in the recovery of C trachomatis in culture.

question

Rickettsiae infecting man multiply preferentially within which of the following cells?

answer

endothelial
Rickettsiae species infect and multiply within vascular endothelial cells.

question

****************Parasites*****************

Artifacts found in a stool specimen that can be confused with ova or cysts are:

answer

pollen grains
Pollen grains are common artifacts in stool specimens submitted for ova and parasite examinations. Their appearance is similar to protozoan cysts.

question

Polyvinyl alcohol used in the preparation of permanently stained smears of fecal material:
serves as an adheasive

answer

serves as an adheasive
Polyvinyl alcohol is an adhesive and is used in the preparation of smears for stains such as trichrome.

question

The method of choice to detect Acanthamoeba sp. from corneal ulcer scrapings is:

answer

blood agar flooded with a 24 hour growth of E coli
The recommended technique for culturing Acanthamoeba is the use of non-nutriant agar seeded with a lawn of E coli. Specimens with suspected Acanthoameoba are inoculated onto a freshly inoculated lawn of E coli, incubated and observed for 7 days. Identification is based on the characteristics patterns of locomotion and morphologic features of the trophic and cystic forms.

question

Primary amoebic encephlitis may be caused by:

answer

Naegleria foweleri
Naegleria foweleri is the etiologic agent of primary amoebic encephalitis.

question

A formed stool is recieved in the laboratory at 3 am for ova and parasite exam . The night shift technologist is certian that the workload will prevent examination of the specimen until 6 am. when the next shift arrives. The technologist should:

answer

preserve the specimen in formalin until it can be examined
Formed stool is unlikely to contain trophozoites so direct examination of the stool is not necessary. The stool should be preserved as soon as possible to preserve any cysts, ova or larvae that may be present in the specimen.

question

A batch of trichrome stained slides for ova and parasite examination for ova and parasite examination contains numerous minute crystals, which totally obscure the microscopic field. Which of the following is the most appropriate remedial action?

answer

Change the iodine alcohol solution to obtain a strong tea-colored solution, restain

Incomplete removal of mercuric chloride may cause the smear to contain refractile crystals. Since the 70% ethanol-iodine solution removes the mercury, it should be changed at least weekly to maintain the strong tes color.

question

The advantage of thick blood smears for malarial parasites is to:

answer

improve detection of the organisms
The increased amount of blood placed on the slide of a thick smear for blood parasites improves the sensitivity of the smear. Thick smears should be preformed on all request for blood parasites.

question

Multifocal brain lesion in AIDS patients is commonly caused by:

answer

Toxoplasma gondii
The most common cause of ring enhansed brain lesions in a patient with HIV-AIDS is Toxoplasma gondii

question

A 44 year old man was admitted to the hospital following a two week history of low grade fever, malaise and anorexia. Examination of a Gemsa stain revealed many intra erythrocytic parasites, Further history revealed frequent camping trips near Mathas vineyard and Nantuckett Island but no travel outside the continental United States. This parasite could easily be confused with

answer

plasmodium falciprum
The patients history is suggestive of babesia infection. Babesia microti ring forms are similar to plasmodium falciprum. A travel history is helpful in determining the cause of infection.

question

A patient is suspected of having amebic dysentary. Upon microscopic examination of a fresh fecal specimen for ova and parasites, the following data were obtained.
a trophazoite of 25 um
progressive , unidirectional crawl
evenly distributed peripherial chromatin
finely granular cytoplasm
This information probably indicates:

answer

Entaomeba histolytica
The trophozoite of entamoeba histilytica ranges in size from 12-60 um, which is significantly larger than Endolimax nana. The nucleus of E histolytica displays evenly distributed peripheral chromotin unlike E coli, which has coarse peripheral chromatin and I butschii, which has none.

question

Refer to the following image:
[image]
Trophozoites of the cyst shown above are likely to:

answer

have slow, undefined motility

Entamoeba coli

question

Refer to the following image:
[image]
Upon finding the above in a fecal concentration, the technologist should:

answer

review the fecal concentration carefully for the presence of other microorganisms that may be pathogenic
(these are found in contamnated water)
Entamoeba coli is a -pathogenic protozoan. its presence indicates the ingestion of fecally contaminated food or water and should lead to a closer review of the specimen for pathogenic parasites or the collection of additional specimens.

question

Refer to the following image:
[image]
An inexperianced parisitology student may confuse the above organism with:

answer

Entaomeba histolytica
(but they only have 4 nucleli)The cysts of Entamoeba coli and E histolytica may appear similar to the unexperianced technologist. E coli cysts are larger and contain more than 4 nuclei in each cyst.

question

Refer to the following image:
[image]
This structure depicts:

answer

a cyst of a nonpathogenic amoeba

question

Refer to the following image:
[image]
the organism depicted is a:

answer

flagellate:

question

Refer to the following image:
[image]
A 24 year old woman, who just returned from vacationing in russia, became ill with steatorrheal diarhea, The above organism was found in her stool. The patient likely is suffering from:

answer

giardiasis

question

A liquid stool specimen is collected at 10:00 pm and brought to the laboratory for culture and ova and parasite examination. It s refrigerated until 10:00 am the next day, when the physician request that the techhnologist look for amoebic trophozoites. The best course of action would be to:

answer

request a new specimen.

question

Protozoan cysts are found in a wet mount of sediment from ethyl- acetate concentrated material.The cyst are without peripherial chromatin on the nuclear membrane. Each cyst has 4 nuclei, and each nucleus has a large karyosome, which appears as a refractile dot. These oval cysts are most likely:

answer

Endolymax nana

question

The term " internal autoinfection" is generally used in referring to infections with:

answer

Strongyloides sterocorlis
Strongolyodies rhabditifoem larve are capable of transforming into filiariform larve (infective form) larva in the intestine, and establishes an auto-infective cycle.

question

The best method to demonstrate the ova of Enterbius vermicularis is:

answer

cellophane tape preparation

question

Proper collection of a sample for recovery of Enterobius vermicularis includes collecting:

answer

a scoth tape preparation from the perianal region

question

A fibrous skin nodule is removed from the back of a patient from central america. A microfliaria seen upon microscopic exam of the nodule is:

answer

Onchocerca volvulus
Onchocerca volvulas is the only microfilaria that is deteccted in the skin snips of patients with raised skin nodules. The microfiliaria of Whicheria, Bruglia and Loa loa are found in the blood.

question

Refer to the following image:
[image]
The egg depicted above is most likely to be found in children suffering from:

answer

perianal itching

question

Refer to the following image:[image]
The specimen of choice for finding the above parasite is:

answer

scotch tape prepration

question

The examination of human feces is no help in the detection of

answer

Echinococcus granulosis

question

The causitive agent of cystercercosis is

answer

Tenia solium

question

Organisms that can be eaisly identified to the species level from the ova in fecal specimens include:

answer

Paragonimus westermani, Hymenolepis nana

question

The scolex of taenia saginata has:

answer

4 suckers

question

When stool examination is negative , the preferred specimen for the diagnosis of paragonimiasis is:

answer

sputum

question

A stool specimen for ova and parasite examination contained numerous rhabditiform larvae. Which factor does not aid in the identification of larvae?

answer

appearance of genital primordium

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