SM SM Antimicrobial Resistance & Stewardship 2

Question 1

Which resistance phenotype is detected by a positive modified carbapenem inactivation method (mCIM) and a negative EDTA-CIM (eCIM)?

Accepted Answer

Serine carbapenemase production such as KPC or OXA-48

Answer

Serine carbapenemases (KPC, OXA-48) are mCIM-positive and eCIM-negative because EDTA chelates zinc and inhibits only metallo-beta-lactamases.

Question 2

Vancomycin-resistant Enterococcus (VRE) expresses the vanA operon. Which cellular change confers resistance?

Accepted Answer

Substitution of D-Ala-D-Ala terminus with D-Ala-D-Lac, reducing vancomycin binding affinity

Answer

The vanA operon encodes enzymes that substitute D-Lac for D-Ala at the peptidoglycan terminus, reducing vancomycin binding affinity 1,000-fold.

Question 3

In PK/PD-guided antibiotic dosing, aminoglycosides are optimally dosed using which pharmacodynamic principle?

Accepted Answer

Concentration-dependent killing: maximize Cmax/MIC ratio

Answer

Aminoglycosides exhibit concentration-dependent killing, meaning efficacy correlates with the peak concentration (Cmax) relative to the MIC, supporting once-daily high-dose regimens.

Question 4

Which method is used to detect inducible clindamycin resistance (iMLSB) in Staphylococcus aureus?

Accepted Answer

D-zone test (D-test) using erythromycin and clindamycin disks

Answer

The D-test places erythromycin and clindamycin disks 15-26mm apart; a flattened D-shaped inhibition zone around clindamycin indicates inducible methylase (erm gene) expression.

Question 5

Which CDC Core Elements of Hospital Antibiotic Stewardship Programs includes accountability?

Accepted Answer

A physician leader responsible for outcomes and stewardship activities

Answer

The CDC specifies a physician leader (often an infectious disease physician) as the accountable leader responsible for stewardship program outcomes.

(SM) Specialist in Microbiology Practice Test

(SM) Specialist in Microbiology Practice Test

SM SM Antimicrobial Resistance & Stewardship 2