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Microbiology BOC Exam Prep Questions and Answers (100% Pass)
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©PREP4EXAMS @2024 [REAL EXAM DUMPS] Wednesday, July 17, 2024 1:27 AMMicrobiology BOC Exam Prep Questions and
Answers (100% Pass)
Proper media for culture of a urethral discharge from a man include:
a sheep blood and phenylethyl alcohol agars b eosin-methylene blue and sheep blood agars
c thioglycollate broth and chocolate agar
d chocolate and modified Thayer-Martin agars - ✔️✔️d chocolate and modified Thayer-Martin
agars
d Chocolate agar and chocolate agar- based selective media should be used for recovery of
Neisseria gonorrhoeae from urethral discharge. Chocolate agar provides the nutrients
required by N gonorrhoeae and selective media contains antimicrobial agents that inhibits
other organisms and permits recovery of pathogenic Neisseria.
A sheep blood agar plate inoculated with 0.001mL of urine grows 70 colonies of
Staphylococcus aureus. How many colony forming units per mL of urine be reported?
a 70
b 700
c 7,000
d 70,000 - ✔️✔️d 70,000
d When 0.001 mL of urine is plated, the growth of one colony is equivalent to 1000 CFU/mL.
Thus 70 colonies is 70,000 CFU/mL.
The lowest concentration of antibiotic that inhibits growth of a test that inhibits growth of a
test organism is the:
a minimum inhibitory concentration
b serum inhibitory concentration
c minimum bactericidal titer
d maximum inhibitory titer - ✔️✔️a minimum inhibitory concentration
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, ©PREP4EXAMS @2024 [REAL EXAM DUMPS] Wednesday, July 17, 2024 1:27 AM
a The MIC is a basic laboratory measurement of the activity of an antibiotic against an
organism. It is the lowest concentration of antibiotic that inhibits visible growth of the
organism. It does not represent the concentration of antibiotic that is lethal to the organism.
Which of the following clean catch urine culture colony counts indicates the patient likely
has a urinary tract infection?
a 10^1 CFU/mL
b 10^3 CFU/mL
c 10^5 CFU/mL
d no growth - ✔️✔️b 10^3 CFU/mL
b Patients with infection often have at least 100,000 bacteria/mL of urine in the bladder.
However one third of young women with symptomatic cystitis have less than 100,000
bacteria/mL of urine. The Infectious Disease Society of America consensus definition of
cystitis is greater than or equal to 1,000 CFU/mL of a uropathogen.
The steam autoclave method of sterilization:
a uses 15 lbs of pressure for 15 minutes
b utilizes dry heat for 20 minutes
c produces a maximum temperature of 100 C
d requires a source of ethylene oxide - ✔️✔️a uses 15 lbs of pressure for 15 minutes
a The traditional gravity displacement steam sterilization cycle is 121°C for 15 minutes at 15
pounds per square inch. Ethylene oxide is an alternative sterilization method.
The expected colony count in a suprapubic urine from a healthy individual is:
a 0 CFU/mL
b 100 CFU/mL
c 1,000 CFU/mL
d 100,000 CFU/mL - ✔️✔️a 0 CFU/mL
a Urine in the bladder is normally sterile. Suprapubic aspiration removes urine directly from
the bladder and yields a specimen free of urethral contamination.
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, ©PREP4EXAMS @2024 [REAL EXAM DUMPS] Wednesday, July 17, 2024 1:27 AM
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(n):
a nonfermenter
b obligate anaerobe
c aerobe
d facultative anaerobe - ✔️✔️d facultative anaerobe
d Facultative anaerobes are organisms that can grow under both aerobic and anaerobic
conditions.
The proper blood-to-broth ratio for blood cultures to reduce the antibacterial effect of serum
in adults is:
a 1:2
b 1:3
c 1:10
d 1:30 - ✔️✔️c 1:10
c Human blood contains substances that may inhibit microbial growth. Diluting blood in
culture broth reduces the concentration of these substances as well as any antibiotics that may
be present. The recommended blood broth ratio is 1:5-1:10. Dilutions less than this may
cause the blood to clot trapping organisms in the clot. Greater dilutions may increase the time
to detection
A penicillin-resistant Neisseria gonorrhoeae produces:
a alpha-hemolysin
b beta-lactamase
c enterotoxin
d coagulase - ✔️✔️b beta-lactamase
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, ©PREP4EXAMS @2024 [REAL EXAM DUMPS] Wednesday, July 17, 2024 1:27 AM
b Antimicrobial resistance in Neisseria gonorrhoeae is widespread. The production of beta-
lactamase (penicillinase) breaks open the beta lactam ring of penicillin, destroying its
activity. Thus, Ngonorrhoeae that produce beta lactamase are resistant to penicillin.
Which selective medium is used for the isolation of gram-positive microorganisms?
a Columbia CNA with 5% sheep blood
b trypticase soy agar with 5% sheep blood
c eosin methylene blue
d modified Thayer-Martin - ✔️✔️a Columbia CNA with 5% sheep blood
a Columbia CNA agar contains colistin and nalidixic acid, which inhibit most gram-negative
organisms. Eosin methylene blue is selective and inhibits gram-positive organisms and
modified Thayer Martin is selective and inhibits gram-positive organisms, gram-negative
bacilli and yeast.
The most sensitive substrate for the detection of beta-lactamases is:
a penicillin
b ampicillin
c cefoxitin
d nitrocefin - ✔️✔️d nitrocefin
d The chromogenic cephalosporin test using nitrocefin is the most sensitive and specific test
for detection of beta lactamase. Acidimetric tests employing penicillin are less expensive, but
not as sensitive, as the nitrocefin assay.
A Staphilococcus aureus isolate has an MIC of 4ug/m: to axacillin. There is uncertainty as to
whether this represents an oxacillin (heteroresistant) resistant strain or a hyperproducer of
beta-lactamase.
Strain Oxacillin Amoxicillin-clavulanic acid
strand A Sus Sus
stand B Sus Res
strand C Res Sus
strand D Res Res
Based on the above results for oxacillin and amoxicillin, which strand is heteroresistant?
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