BOC Microbiology Exam Study Set2-Questions with
100% Correct Answers | Verified
The lowest concentration of antibiotic that inhibits growth of a test organism:
Minimum inhibitory concentration
Serum inhibitory concentration
Minimum bactericidal titer
Maximum inhibitory titer - ✔✔Minimum inhibitory concentration
Which of the following clean catch urine culture colony counts indicates the patient
likely has a urinary tract infection?
10¹ CFU/mL
10³ CFU/mL
10⁵ CFU/mL
No growth - ✔✔10³ CFU/mL
The steam autoclave method of sterilization:
Uses 15 lbs of pressure for 15 minutes
Utilizes dry heat for 20 minutes
Produces a maximum temperature of 100°C
Requires a source of ethylene oxide - ✔✔Uses 15 lbs of pressure for 15 minutes
,The expected colony count in a suprapubic urine from a healthy individual is:
0 CFU/mL
100 CFU/mL
1,000 CFU/mL
100,000 CFU/mL - ✔✔0 CFU/mL
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):
Nonfermenter
Obligate anaerobe
Aerobe
Facultative anaerobe - ✔✔Facultative anaerobe
A penicillin-resistant Neisseria gonorrhoeae produces:
Alpha-hemolysin
Beta-lactamase
Enterotoxin
Coagulase - ✔✔Beta-lactamase
Which selective medium is used for the isolation of gram-positive microorganisms?
Columbia CNA with 5% sheep blood
,Trypticase soy agar with 5% sheep blood
Eosin methylene blue
Modified Thayer-Martin - ✔✔Columbia CNA with 5% sheep blood
The most sensitive substrate for the detection of beta-lactamase is:
Penicillin
Ampicillin
Cefoxitin
Nitrocefin - ✔✔Nitrocefin
An Enterococcus isolated from multiple blood cultures in a patient endocarditis should
be:
Screened for high level aminoglycoside resistance
Checked for tolerance
Assayed for serum antimicrobial activity
Tested for beta-lactamase production - ✔✔Screened for high level aminoglycoside
resistance
In the Kirby-Bauer disc diffusion susceptibility test, which variable is critical when testing
Pseudomonas species for antibiotic susceptibility to aminoglycosides?
Incubation temperature
Duration of incubation
Cation content of media
, Depth of agar - ✔✔Cation content of media
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
tests to obtain the following results:
TSI: acid butt, alkaline slant, no gas, no H2S
phenylalanine deaminase: neg
Motility: pos
Serological typing: Shigella flexneri (Shigella subgroup B)
The serological typing is verified with new kit and controls. The best course of action
would be to:
Report the organism of Shigella flexneri without further testing
Verify reactivity of motility medium with positive and negative controls
Verify reactivity of the TSi slants with positive and negative controls for H₂S production
Verify reactivity of phenylalanine deaminase with positive and negative controls -
✔✔Verify reactivity of motility medium with positive and negative controls
Susceptibility testing performed on quality control organisms using a new media lot
number yielded zone sizes that were too large for all antibiotics tested. The testing was
repeated using media from a previously used lot number, and all zone sizes were
acceptable. Which of the following best explains the unacceptable zone sizes?
The antibiotic disks were not stored with the proper desiccant
The depth of the media was too thick
The depth of the media was too thin
100% Correct Answers | Verified
The lowest concentration of antibiotic that inhibits growth of a test organism:
Minimum inhibitory concentration
Serum inhibitory concentration
Minimum bactericidal titer
Maximum inhibitory titer - ✔✔Minimum inhibitory concentration
Which of the following clean catch urine culture colony counts indicates the patient
likely has a urinary tract infection?
10¹ CFU/mL
10³ CFU/mL
10⁵ CFU/mL
No growth - ✔✔10³ CFU/mL
The steam autoclave method of sterilization:
Uses 15 lbs of pressure for 15 minutes
Utilizes dry heat for 20 minutes
Produces a maximum temperature of 100°C
Requires a source of ethylene oxide - ✔✔Uses 15 lbs of pressure for 15 minutes
,The expected colony count in a suprapubic urine from a healthy individual is:
0 CFU/mL
100 CFU/mL
1,000 CFU/mL
100,000 CFU/mL - ✔✔0 CFU/mL
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):
Nonfermenter
Obligate anaerobe
Aerobe
Facultative anaerobe - ✔✔Facultative anaerobe
A penicillin-resistant Neisseria gonorrhoeae produces:
Alpha-hemolysin
Beta-lactamase
Enterotoxin
Coagulase - ✔✔Beta-lactamase
Which selective medium is used for the isolation of gram-positive microorganisms?
Columbia CNA with 5% sheep blood
,Trypticase soy agar with 5% sheep blood
Eosin methylene blue
Modified Thayer-Martin - ✔✔Columbia CNA with 5% sheep blood
The most sensitive substrate for the detection of beta-lactamase is:
Penicillin
Ampicillin
Cefoxitin
Nitrocefin - ✔✔Nitrocefin
An Enterococcus isolated from multiple blood cultures in a patient endocarditis should
be:
Screened for high level aminoglycoside resistance
Checked for tolerance
Assayed for serum antimicrobial activity
Tested for beta-lactamase production - ✔✔Screened for high level aminoglycoside
resistance
In the Kirby-Bauer disc diffusion susceptibility test, which variable is critical when testing
Pseudomonas species for antibiotic susceptibility to aminoglycosides?
Incubation temperature
Duration of incubation
Cation content of media
, Depth of agar - ✔✔Cation content of media
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
tests to obtain the following results:
TSI: acid butt, alkaline slant, no gas, no H2S
phenylalanine deaminase: neg
Motility: pos
Serological typing: Shigella flexneri (Shigella subgroup B)
The serological typing is verified with new kit and controls. The best course of action
would be to:
Report the organism of Shigella flexneri without further testing
Verify reactivity of motility medium with positive and negative controls
Verify reactivity of the TSi slants with positive and negative controls for H₂S production
Verify reactivity of phenylalanine deaminase with positive and negative controls -
✔✔Verify reactivity of motility medium with positive and negative controls
Susceptibility testing performed on quality control organisms using a new media lot
number yielded zone sizes that were too large for all antibiotics tested. The testing was
repeated using media from a previously used lot number, and all zone sizes were
acceptable. Which of the following best explains the unacceptable zone sizes?
The antibiotic disks were not stored with the proper desiccant
The depth of the media was too thick
The depth of the media was too thin
