Mechanisms of Abx Resistance

Question 1

5 Mechanisms of Abx Resistance

Answer 1

Altered targets
Bypass inhibited pathways
Abx inactivation 
Decreased influx
Increased Efflux

Question 2

Altered Targets

Answer 2

PBP enzyme (beta-lactam resistance)
Ribosomal subunit (tetracycline resistance - sim amino glycoside, lincosamide, macrolide resist.)
DNA gyrase/Topoisomerase IV (quinolone resistance)
Peptidoglycan precursors (vancomycin resistance)
DHPS/DHFR enzymes (Sulfonamide trimethroprim resistance)

Question 3

Bypass inhibited pathway

Answer 3

Enterococcus can scavenge preformed folic acid invivo

- doesn’t require own folate metabolic pathway

Question 4

Antibiotic Inactivation

Answer 4

Beta-lactamases (“cleaves” to inactivate)
- penicillinase, cephalosporinase, carbapenemase
Aminoglycoside modifying enzymes (“adds” to inactivate)

Question 5

Decreased influx/permeability

Answer 5

Ex. Meropenem resistance (similar amino glycoside resistance)

• via decreased number of channels
  ex. in Pesudomonas aeruginosa

Question 6

Increased Efflux

Answer 6

Multidrug efflux pump systems in P. aeruginosa