SM Antimicrobial Resistance & Stewardship Flashcards

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

Answer: Serine carbapenemase production such as KPC or OXA-48

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

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

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

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

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

Answer: Concentration-dependent killing: maximize Cmax/MIC ratio

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

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

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

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.

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

Answer: A physician leader responsible for outcomes and stewardship activities

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

A hospital antibiogram shows 40% susceptibility of E. coli to fluoroquinolones. According to stewardship guidelines, what is the recommended action for empiric UTI therapy?

Answer: Avoid fluoroquinolones for empiric therapy and choose an alternative agent

IDSA guidelines recommend avoiding antibiotics with <80% susceptibility on the local antibiogram for empiric UTI therapy to ensure adequate treatment.