Veterinary Bacteriology: Test 1 old exam questions – Flashcards
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Unlock answers| Using the nomenclature of the A-B model for binary toxin structure, the B subunit of anthrax toxin would most closely correspond to... |
protective antigen (edema factor and lethal factor would be A / active subunit)
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| The principal polymer structure of a bacterial cell wall (peptidoglycan) acquires most of its strength at a final step in the synthesis that involves crosslinking through... |
N glycosidic linkages bind at penultimate AA and cleave it off to acheive strong bond |
| Would the involvement of an integron as a mechanism of multidrug resistance be more likely in e coli (Gram -) or in s aureus (Gram +) ? |
e coli |
| True or false: In an individual animal, a positive test for antibodies against a pathogen is always indicative of an infection. |
FALSE infection could have already passed |
| True or False: In an individual animal, disease is always a consequence of infection |
FALSE carriers, normal flora, etc |
| Disease prevalence usually has the greatest impact on which property of testing? |
| Positive predictive value |
| The Beta lactam ring found in all penicillin and cephalosporin antibiotics has the greatest structural homology with |
Terminal alanine dipeptides in peptidoglycan (gram + peptidoglycan)
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| When bacteria are actively growing, their numbers increase in what fashion? |
| logarithmically |
| T/F: Prokaryotic and eukaryotic organisms can possess a cell wall |
true fungi are eukaryotes that have cell walls |
| T/F Prokaryotic and eukaryotic organisms replicate by mitosis |
FALSE bacteria replicate by binary fission |
| The conditions employed for destruction of endospores in an autoclave are.. |
121 C for 15 minutes high pressure is also used heat is provided by steam (hot air would take much longer to sterilize) |
| T/F Germination of bacterial endospores is dependent on an activating factor that ends the state of dormancy and may cause slight damage to the spore coat |
| TRUE |
| Germination of bacterial endospores is dependent on an intiating factor that causes degradation of the ______ _____ and _____, ______ of ________ and release of _____ and _______ acid. |
| spore coat and cortex, absoption of water and release of calcium and dipicolinic acid |
| Peptidoglycan is associated with Gram +, Gram -, or both? |
BOTH Gram + has more |
| Teichoic acid is found in Gram |
| positive |
| Gram + and - have plasmids that encode for _____ ______ |
| antibiotic resistance |
What does NOT limit the commercial development of lytic bacterial viruses to combat bacterial infections in animals?
a)poor immunogenicity of bacterial viruses
b) host specificity of bacterial virus
c) potential trasnfer of bacterial genes from a pathogen to a non-pathogen d) metaboilic activity of bacterial viruses |
| A |
The MIC (minimum inhibitory concentration) of an antimicrobial drug for a bacterium is usually expressed in which unit? |
| micrograms per milliliter |
The best choice of media for isolation of a fastidous bacterial pathogen is |
chocolate agar does not have chocolate! blood that has bascially been cooked for the bacteria not a selective medium fastitidous = picky eater
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Bacteria with storage granules (cytoplasmic inclusions) will have a ______ with methylene blue or Gram's stain |
beaded filament appearance uneven staining |
____ developed his ideas about germ theory of disease by inoculating animals with ATTENUATED ORGANSISMS |
| Pasteur |
Specimen transport and storage: diagnostic specimens should be placed in ____ ______ for transport |
two containers (should be well sealed) |
The greatest weakness of antibody detection as a means of diagnosing bacterial disease is... |
antibodies are indicative of antigen exposure could be not disease or not current disease |
Feature of _______ that differentiates them from insertion sequences, is a possession of terminal invert repeat sequences:
a) transposons
b)integrons c)both
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| B |
Feature of _______ that differentiates them from insertion sequences, is the ability to readily move across some distance in a cell form one DNA molecule to another:
a)integrons
b)transposons C)both
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| B |
Feature of _______ that differentiates them from insertion sequences, is possession of a strong generic promoter sequence:
a)integrons
b)transposons c) both
|
| A |
Feature of _______ that differentiates them from insertion sequences, is association with antibiotic resistance: a) integrons
b)transposons c)both
|
C |
Trace metal that is required in greatest abundance for growth of bacteria is... |
| IRON |
Lingering bacterial inhibition in the body after antimicrobial drug levels disappear is.... |
Post-antibiotic effect |
Dependency on fermentation as a means of generating energy from carbohydrate substrates is greatest among... |
Obligately anaerobic bacteria
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Methicillin resistance in Staphylococcus species is usually indicative of... |
resistance to all beta lactams mecA gene! |
Chronic and recurrent forms of canine pyoderma caused by Staphylococcus pseudintermedius are often complicated by... |
hypersensitvity and immune complexes skin barriers are weakened |
Fluid and electrolyte replacement is most critical to individual patient care during |
diarrheal disease caused by enteric infections.
|
Bacillus anthracis requires ________ for capsular production. |
carbon dioxide heat |
________ infections are acquired within hospitals |
| nosocomical |
The principal function of lysozyme in the mucosal lining of the GI tract is to ___________ |
destroy bacterial cells (breaks glycosidic bond in peptidoglycan) |
When an antibiotic drug molecule binds to the target macromolecule associate with its antibacterial action in a bacterial cell, the drug is _____________ and unavailable to bind to _________________________-. |
irreversibly bound; other bacterial targets (1st order rate kinetics) |
Severe intestinal disease that develops in some patients after administration of a broad-spectrum antibiotic is most likely the result of an _______________________________ |
imbalance of the normal bacterial flora caused by the antibiotic |
| T/F infectious disease is the same thing as communicable disease |
| FALSE |
When not causing disease, Streptococcus equi subspecies equi is likely to persist for the longest period of time in ___________________-- |
asymptomatic animal carriers. guttural pouch |
A positive predictive value is... |
| the likelihood that a positive test result is a true positive |
A flagellar filament is composed of... |
a polymer of a single protein subunit. |
Many strains of staphylococcus aureus express a plasminogen activator that causes dissolution of fibrin clots. This product is called |
staphylokinase |
The _____ (organ) is most active in removing bacteria from the blood stream |
| spleen |
The O antigens of Gram negative bacteria are protective against ___________. |
complement mediated lysis |
_______________- is part of the repeated subunit structure of BOTH lipid A AND peptidoglycan. |
N-acetyl glucosamine |
Two of the most important safety concepts that should be addressed when shipping or internally transporting infectious substances are: |
secondary containment and external package hazard communication |
When selecting a drug to use, choose the one that has the zone of inhibition______________ |
that is the largest larger zone diameter is more likely to be susceptible |
Intuitively, one would expect that gram ______ bacteria are preferentially more susceptible than gram______ bacteria to drugs that inhibit membrane function. |
negative; positive less osmotic stability in gram - |
Insertion of a________________- into a chromosomal bacterial toxin gene is most likely to result in toxin gene inactivation. |
| lysogenic bacteriophage |
Once initiated, bacterial endospore production usually requires |
| 8-10 hours |
The process of creating a live, relatively harmless and usually stable form of a pathogenic bacterium is called? |
| attenuation |
In an iron-restricted environment, pathogenic Staphylococcus sp. Are able to grow faster than less pathogenic Staphylococcus sp. Due to their ability to up-regulate genes that encode? |
siderophores this was multiple choice; another option not listed could be hemolysis and heme binding |
Side chain substitutions in members of a particular class of antimicrobial drugs are LEAST likely to affect…. |
Mode of action of drug on bacteria |
The role of agar in bacterial growth is best described as… |
Non-nutritional support matrix |
A bacterium that has a high MIC for a particular drug… (Minimum Inhibitory Concentration) |
Is likely to be refractory to usual treatments w/ the drug during infection |
A property of the stratum corneum that enhances the antimicrobial barrier functions of skin is… |
| antibacterial lipids |
C3b, the cleavage product of the third component of complement, is of central importance to the host, especially against invasive infections caused by capsulated bacteria because it… |
Enhances phagocytosis in the absence of bacteria-specific antibodies complement is able to act without recognzing a specific antigen (it is part of innate immunity) recognises PAMPs (pathogen associated molecular patterns) |
A chronic pyogranulomatous process involving subcutaneous tissues of the foot in birds is commonly associated w/ staphylococcus aureus infection. This condition is called… |
| bumblefoot |
Cellular stimulation through non-specific binding to T lymphocyte receptors and macrophage major histocompatibility complex proteins best describes the mode of action of… |
Staphylocococal toxic shock syndrome toxin |
If an assay measures bacterial growth endpoints in broth as the change in visible opacity from clear to turbid, the highest (and most sensitive) final concentration of the starting bacterial inoculum that would be suitable is… |
5x10^5 cfu/ml |
Global (transcriptional) regulation of many genes involved with staphylococcal disease is triggered by… |
Staphylococcal population density (Quorum sensing) |
The best empirical drug choice for treating a severe infection caused by methicillin resistant Staphylococcus aureus would be… |
Vancomycin (a narrow spectrum, glycopeptide antibiotic) same mechanism as beta lactams (cell wall synthesis) but not the same chemical structure |
Clavulanic acid is known primarily as a… |
Beta lactamase inhibitor administered along with drug |
It is often recommended that the duration of antimicrobial treatment for an acute infection should be… |
Continued for 48 hours after disappearance of symptoms
|
Acidic Polysaccharide polymers of glycerol or ribitol phosphate… |
(teichoic acids) Are major surface antigens of many Gram positive bacteria |
Myeloperoxidase is an enzyme that is useful in… |
Oxygen dependent bacterial killing in phagolysosomes other oxygen dependent enzymes: NADPH oxidase, superoxide dismutase oxygen independent: pH, lysozyme, cationic proteins, lactoferrin, vitamin B12 binding protein, acid hydrolases |
Integrons are most frequently associated w/… |
| antibacterial resistance |
As commonly performed, the color of gram-positive bacteria in a Gram stain smear is |
PURPLE crystal violet stain gram negative is pink/red: safranin |
Alcohol based handwashing solutions should be used… |
BEFORE EATING not for endospores, they will resist it's not a replacement for sterile gloves don't use it when hands are visibly soiled because it will not rinse away dirt and your hands will not be clean at all! washing and rinsing is actually more effective than alcohol or other chemicals if there is solid matter present b/c they can't penetrate the dirt/poop/whatever. it's the same on inanimate objects like cages |
Tissue necrosis seen in gangrenous forms of mastitis caused by Staphylococcus aureus is attributed to staphylococcal… |
| ALPHA TOXIN |
The minimum inhibitory concentration (MIC) of an organism for a particular drug is equivalent to its minimum bactericidal concentration (MBC) for the same drug |
No. The MIC is how much to inhibit growth, not to kill the bacteria (MBC). there might still be viable bacteria in the solution at MIC. |
If an abscess is not drained, live bacteria contained within the pus will escape into the surrounding tissues and blood stream |
Not necessarily true, in the case of a long standing absess, usually the area is walled off by fibrin from surrounding tissue. Pus is an accumulation of dead leukocytes and thus is drained out of the body |
Isolation of numerous microorganisms from a normally sterile body site without the presence of inflammatory cells should be viewed with suspicion. |
True, microorganisms that should not be present should trigger an immune response, if they do not, test that isolated them should be examined |
Plasmids are transferred between bacteria via bacteriophage
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This is not true, some plasmids can transfer themselves, bacteriophages can transfer information by packaging some of DNA from a host cell and injecting it (generally or specifically) into a 2nd bacteria (plasmids can be conjugative, mobilizing or non mobilizing - not all transfer themselves but none are transferred by bacteriophage)
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A bacterial isolate that grows in the absence of oxygen is classified as an anaerobe. |
This is not necessarily true, there are also facultative anaerobes which can tolerate oxygen and can also grow without. It is not strictly just an anaerobe. |
Bacteria can be visualized by bright-field microscopy using 100x oil-immersion objective. |
Not true, to see bacteria following staining one should use a 1000x magnification as bright field only shows bacteria up to .2 um in size. |
Disease is not an inevitable consequence of infection. |
True, infection can be carried by a chronic patient and shed into the environment w/out the carrier actually being sick. Also bacteria can live in a state of lysogeny w/ bacteriophages and not be “sick” until lysogeny ends. |
Fimbriae (pilli) have specialized function in bacterial gene transfer. |
True - sex pilli are formed from a donor cell and 1 strand of DNA is transferred, at which time another complementary strand is synthesized. |
Give one example of an activity that supports the philosophy of “prudent use of antimicrobials” in order to control population wide antimicrobial resistance |
Working to improve compliance in affected patients, if someone does not finish a route of antimicrobials, they have chance of illness again because the disease could come back and be more resistant after mutation (education) (prudent use of drug) |
In a laboratory bacterial killing assay, Penicillin G at a concentration of .3 micrograms/ml caused a 99.9% reduction in bacterial numbers. However, in the same assay with the same inoculum, penicillin G at a concentration of 300 micrograms/ml caused only 10% reduction in bacterial numbers. Bacteria that survived the drug treatments, when retested, were susceptible to penicillin G and were indistinguishable from the original bacterial population.
• What is the principal mode of action of penicillin G on bacteria? • How could the bactericidal action of penicillin G be negated by increasing concentrations of the drug, without changing the inherent properties of the bacterium?
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1: Disrupts the cell wall by not allowing cross-linking of peptidoglycan (correct) more info - this only happens during development; not to fully grown bacteria
2: Pharmokinetics follows 1st rate order kinetics, meaning 1 molecule of drug is consumed for every 1 receptor, all receptors could be bound with drug, yielding no response when penicillin concentration elevates.(partial credit) real answer: penicillin only works on actively growing populations! if you've killed off the majority of the growing bacteria quickly, then the population is not actively growing. thus a higher concentration of the drug is actually less effective in killing bacteria
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