SM SM Antimicrobial Resistance & Stewardship

Question 1

Which mechanism does Staphylococcus aureus use to confer resistance to beta-lactam antibiotics including methicillin?

Accepted Answer

Expression of altered penicillin-binding protein PBP2a encoded by mecA

Answer

Production of beta-lactamase that hydrolyzes the antibiotic

Answer

Active efflux of the antibiotic via MexAB-OprM pump

Answer

Reduced outer membrane permeability preventing drug entry

Question 2

Which phenotypic test is used in clinical microbiology labs to screen for extended-spectrum beta-lactamase (ESBL) production in Enterobacteriaceae?

Accepted Answer

Double-disk synergy test using clavulanate and cephalosporins

Answer

Carbapenem inactivation method (CIM)

Answer

Modified Hodge test

Answer

Colistin broth disk elution

Question 3

A Klebsiella pneumoniae isolate tests resistant to all carbapenems and is positive on the carbapenem inactivation method (CIM). Which resistance mechanism is most likely?

Accepted Answer

KPC (Klebsiella pneumoniae carbapenemase) production

Answer

OXA-48 serine carbapenemase production

Answer

NDM (New Delhi metallo-beta-lactamase) production

Answer

Loss of porin OmpK35/OmpK36 combined with AmpC overexpression

Question 4

According to antimicrobial stewardship principles, which intervention most effectively reduces unnecessary broad-spectrum antibiotic use?

Accepted Answer

Prospective audit and feedback by infectious disease-trained pharmacists

Answer

Automatic stop orders after 72 hours for all antibiotics

Answer

Restricting vancomycin to ID physician approval only

Answer

Posting antibiogram data in nursing units

Question 5

Which of the following correctly describes horizontal gene transfer of resistance genes via conjugation?

Accepted Answer

Direct cell-to-cell transfer of plasmids through a pilus

Answer

Transfer of DNA through bacteriophage between bacteria

Answer

Uptake of naked DNA from the environment

Answer

Transposon insertion within the bacterial chromosome

Question 6

The minimum inhibitory concentration (MIC) of an antibiotic is best defined as:

Accepted Answer

The lowest concentration that visibly inhibits bacterial growth

Answer

The concentration that kills 99.9% of bacteria in 24 hours

Answer

The concentration at which bactericidal activity begins

Answer

The serum drug level achievable at standard dosing