question

Bordetella

answer

o clinical presentation
During paroxysmal phase: leukocytosis (>50000 cells/μL, normal is 4500-11000); nasopharyngeal swab: gram stain may be difficult because low number of organisms; culture: bordet-genou media (within 3 – 7 days; serological: direct fluorescent antibody test, antibodies against the toxins

question

NG

answer

 Males: numerous PMNs containing organism
 Females: + GC culture
 If bacteremiaculture skin, joint fluid, blood
 oxidase+
 ferments glucose but not maltose
 aerobic growth with enhancement with 5% CO2
 chocolate agar
 Thayer-Martin medium
 Rapid NAATs (nucleic acid amplification tests)

question

NM

answer

 encapsulated in CSF and blood
 transparent, non-pigmented non-heme on chocolate with 5% CO2
 Thayer-Martin agar
 oxidase+
 fermentation of glucose and maltose

question

Escherichia

answer

 G- rods, oxidase-, cat+
 Lactose fermenters: pink on MacConkeys
 EHEC: does not ferment sorbitol (detected on MacConkeys sorbitol agar)
 Antigenic structure: O, K, H (O157:H7)

question

Salmonella

answer

 Isolation of bacteria from blood, feces, urine, left over foods
• Bile salts inhibit Gram + and most other Enterobacteriaceae
• Salmonella-Shigella media: Thiosulfate and citrate used to indicate H2S production during glucose fermentation: colonies with black centers

question

Shigella

answer

 isolation from feces on Salmonella-Shigella media

question

Y. pestis

answer

• clinical presentation
• gram stain; growth on MacConkey agar

question

Y. enterolotica and pseudotuberculosis

answer

• obtained from stool sample
• isolation on MacConkey at 4 C
• Serological testing: anti-Yersinia antibodies

question

Vibrio

answer

 Rice water – V. cholera O1 or O139
 Gram stain of stool difficult
 Direct fluorescent antibody test of stoll
 Media:
• alkaline peptone broth
o survive and replicate at high pH
o selective
• Thiosulfate citate bile salts sucrose (TCBS) agar
o selective/differential
 V. cholera grow yellow
 Biochemical and serological tests

question

Aeromonas

answer

 oxidase +
 beta hemolysis

question

Campylobacter

answer

 gull-wing appearance in gram stain
 darting motility (characteristic)
 culture on special media with antibiotics that inhibit normal flora
 Catalase, oxidase, and hippurase +

question

Helicobacter

answer

 gastric biopsy
 urease, catalase, and oxidase+
 serum antibodies
 Urease breath test: patient ingests radioactive labeled urea: if microbe is present, urea will be split into ammonia and CO2radioactive –labeled CO2 detected upon exhalation

question

Pseudomonas

answer

o non-selective media
 creamy colonies on MacConkeys agar: does not ferment lactose
o beta hemolysis
o oxidase and catalase +
o pigment production: blue or yellow-green
o fruity odor: characteristic

question

Haemophilus

answer

o gram stain: pleomorphic, gram – coccobacilli
o X and V factors on chocolate agar
o type b capsule detection
o nucleic acid analysis

question

o F. tularensis

answer

 slow growth (2-10 days) on chocolate or buffered charcoal yeast extract (BCYE), both supplemented with cysteine
 agglutination with specific antibodies
 antibody titer

question

o B. melitensis

answer

 slow growth (3 days to weeks) on blood agar
 oxidase, catalase, and urease +
 antibody detection

question

Leginonella

answer

o 2-5 days on BCYE, not blod or chocolate: must have cysteine and iron, amino acids (does not use carbs), charcoal absorbs toxic fatty acids, pH (6.9)
o direct fluorescence antibody test

question

Bartonella quintana

answer

Culture of special media with patient antibodies

question

o C. perfringens

answer

 clinical presentation
 absence of WBCs and G+ rods
 rapid (<1 day) growth on blood agar with double zone of hemolysis: theta (inner beta hemolysis) and alpha (outer hemolysis)
 nagler reaction: hydrolysis of phospholipids in egg yolk agar
 detection of high number of bacteria in food or feces
 detection of enterotoxin

question

o C. difficile

answer

 clinical symptoms and toxins in feces

question

o C. tetani

answer

 clinical presentation
 difficult to culture: small number of organisms, killed by O2
 difficult to detect toxin or antibodies in patient: toxin is internalized by neurons

question

o C. botulinum

answer

 clinical presentation
 Food borne: toxin detected in food or patient serum, feces or gastric fluid
 Infant: toxin detected in feces or serum
 Wound: toxin detected in serum or wound

question

Actinomyces israeli

answer

o clinical symptoms, history of trauma, slowly progressive course
o lab diagnosis can be difficult: part of normal flora, slow growers, anaerobic
o presence of sulfur granules: gram stain
o culture: takes 1-2 weeks to see growth under anaerobic conditions: distinctive colony morphology

question

Spirochete general

answer

 difficult to grow
 difficult to visualize with light microscopy because do not stain well and/or very thing
• darkfield, immunofluorescence or special stains

question

T. pallidum

answer

 do not grow in cell-free cultures: not routinely cultured in lab
 requires immunofluorescent or dark-field microscopy
 nontrepenomal screening tests
• detects nonspecific antibody, reagin, that reacts with cardiolipin (phospholipid found in beef heart tissue): inexpensive
• flocculation tests: consist of adding cardiolipin to patient’s serum
o positive: cardiolipin forms into fine aggregates/floccules
o other diseases may give positive reactions
o all positive sera must be retested to confirm with specific treponemal tests
 treponemal tests
• FTA-ABS (fluorescent treponemal antibody – absorbed): freeze-dried organism fixed to slide
o patient serum is added
o slide is rinsed, covered with fluorescent-labeled abs against human Ig
o positive=spirochete-fluorescent ab complex fluoresces
• Particle agglutination test
o antigens on gelatin particles are mixed with patient serum: specific abs will cause particles to agglutinate

question

B. burgdorferi

answer

 early disease: clinical presentation, especially rash (no antibodies yet)
 late disease : patient antibodies (false positives)

question

B. recurrentis

answer

 clinical presentation
 appearance of Giemsa-stainable, loosely coiled spirochetes in blood during febrile stage

question

o L. interrogans

answer

 sensitive to drying and many disinfectants
 survival in slightly alkaline water for weeks
 difficult to visualize
 slow growth on specialized media: 2 weeks to 4 monts
 serological agglutination test

question

Mycoplasma pneumoniae

answer

Staining: poor or not at all
• Absence of organisms may be suggestive
– Sputum analysis: scanty and nonpurulent
• Cultured on special agar, 1-6 weeks
– High antibody titer

question

M. hominis

answer

requires arginine, fried egg colonies

question

M. genitalium

answer

difficult to culture at all

question

U. urealyticum

answer

requires urea and buffered media

question

R. rickettsii

answer

clinical grounds; Giemsa or Gimenez stain; serology: indirect fluorescent antibody test for patient antibodies against OmpA; Direct fluorescent antibody test; PCR based tests

question

R. akari

answer

indirect immunofluorescence antibody test

question

R. prowazekii

answer

Serology: Epidemic typhus (IgM followed by IgG antibodies); Brill-Zinsser (IgG anamnestic response)

question

R. typhi

answer

Serology: indirect fluorescent antibody test

question

Ehrlichia and Anaplasma

answer

Leukopenia, thrombocytopenia, elevated serum tranaminases; microscopic observation of morulae in blood smears (rare for HME, possible for HGA); culture rare; serology common; DNA probes available

question

Coxiella burnetti

answer

Serology: acute (antibody to phase II); chronic (antibody to phase I and II)

question

C. trachomatis

answer

Culture: staining inclusions, specific but not sensitive; antigen detection (ELISA or IF): group specific LPS, stain specific outer membrane proteins; serology: cannot distinguish between current or past infection, detection of high titer IgM antibodies can be helpful; NAATs

question

Chlamydophila psittaci

answer

fourfold rise in titer

question

Chlamydophila pneumoniae

answer

fourfold rise in titer

question

B. henselae

answer

pt. antibodies

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