BOC MICROBIOLOGY EXAM 1 QUESTIONS
WITH COMPLETE QUESTIONS AND
ANSWERS [ GRADED A+]
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
The proper blood-to-broth ratio for blood cultures to reduce the antibacterial
effect of serum in adults is:
©morren2024/2025.Year published 2024.
,a. 1:2
b. 1:3
c. 1:10
d. 1:30 - ✔✔c. 1:10
The most sensitive substrate for the detection of beta-lactamases is:
a. penicillin
b. ampicillin
c. cefoxitin
d. nitrocefin - ✔✔d. nitrocefin
A Staphylococcus aureus isolate has an MIC of 4ug/mL to oxacillin. There is
uncertainty as to whether this represents an oxacillin (heteroresistant) resistant
strain or a hyperproducer of beta-lactamase.
Based on the below results for oxacillin and amoxicillin-clavulanic acid, which
strain is heteroresistant?
©morren2024/2025.Year published 2024.
,Strain Oxacillin Amoxicillin-clavulanic acid
Strain A susceptible susceptible
Strain B susceptible resistant
Strain C resistant susceptible
Strain D resistant resistant - ✔✔d. Strain D: resistant to both Oxacillin and
amoxicillin-clavulanic acid
-Resistant to all beta-lactam agents and combinations
An Enterococcus isolated from multiple blood cultures in a patient endocarditis
should be:
a. screened for high level aminoglycoside resistance
b. checked for tolerance
c. assayed for serum antimicrobial activity
d. tested for beta-lactamase production - ✔✔a. screened for high level
aminoglycoside resistance
©morren2024/2025.Year published 2024.
, The procedure that assures the most accurate detection of mecA-mediated
oxacillin resistance in routine broth microdilution susceptibility testing against S.
aureus is:
a. addition of 4% NaCl
b. incubation at 30'C
c. incubation for 48 hours
d. use of cefoxitin for testing - ✔✔d. use of cefoxitin for testing
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 obstain the following results:
TSI: acid butt, alkaline slant, no gas, no H2S
Phenylalanine deaminase: negative
motility: positive
serological typing: Shigella flexneri (Shigella subgroup B)
©morren2024/2025.Year published 2024.
WITH COMPLETE QUESTIONS AND
ANSWERS [ GRADED A+]
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
The proper blood-to-broth ratio for blood cultures to reduce the antibacterial
effect of serum in adults is:
©morren2024/2025.Year published 2024.
,a. 1:2
b. 1:3
c. 1:10
d. 1:30 - ✔✔c. 1:10
The most sensitive substrate for the detection of beta-lactamases is:
a. penicillin
b. ampicillin
c. cefoxitin
d. nitrocefin - ✔✔d. nitrocefin
A Staphylococcus aureus isolate has an MIC of 4ug/mL to oxacillin. There is
uncertainty as to whether this represents an oxacillin (heteroresistant) resistant
strain or a hyperproducer of beta-lactamase.
Based on the below results for oxacillin and amoxicillin-clavulanic acid, which
strain is heteroresistant?
©morren2024/2025.Year published 2024.
,Strain Oxacillin Amoxicillin-clavulanic acid
Strain A susceptible susceptible
Strain B susceptible resistant
Strain C resistant susceptible
Strain D resistant resistant - ✔✔d. Strain D: resistant to both Oxacillin and
amoxicillin-clavulanic acid
-Resistant to all beta-lactam agents and combinations
An Enterococcus isolated from multiple blood cultures in a patient endocarditis
should be:
a. screened for high level aminoglycoside resistance
b. checked for tolerance
c. assayed for serum antimicrobial activity
d. tested for beta-lactamase production - ✔✔a. screened for high level
aminoglycoside resistance
©morren2024/2025.Year published 2024.
, The procedure that assures the most accurate detection of mecA-mediated
oxacillin resistance in routine broth microdilution susceptibility testing against S.
aureus is:
a. addition of 4% NaCl
b. incubation at 30'C
c. incubation for 48 hours
d. use of cefoxitin for testing - ✔✔d. use of cefoxitin for testing
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 obstain the following results:
TSI: acid butt, alkaline slant, no gas, no H2S
Phenylalanine deaminase: negative
motility: positive
serological typing: Shigella flexneri (Shigella subgroup B)
©morren2024/2025.Year published 2024.
