Antimicrobial Resistance

Question 1

3 Major Mechanisms of Resistance

Answer 1

Inactivating/Modifying the Drug
Altering the target
Reducing the ability of the drug to reach the target

Question 2

Mechanisms of Beta Lactam Resistance (3)

Answer 2

Modifying the drug w/ beta lactamase
Modifying the target by changing PBPs
Making PBPs harder to reach (intrinsic)

Question 3

3 Narrow Spectrum Beta Lactamase Genes

Answer 3

Bla, plasmid, Staph
TEM-1, plasmid, E Coli
SHV-1, chromosome, Klebs

Question 4

2 Main Organisms w/ Extended Spectrum Beta Lactamases

Answer 4

E Coli and Kelbs (best at taking up plasmids)

Question 5

Which organisms have AmpC gene? (ESBL)

Answer 5

Pseudomonas and Enterobacter

Question 6

Inducers of AmpC

Answer 6

Ampicilin and Cephazolin

Question 7

How do we treat AmpC bugs?

Answer 7

Carbapenems

Question 8

Carbapenemases (2) and associated organisms

Answer 8

KPC and NDM-1

Enterobacter, E Coli, and Klebs

Question 9

2 ways to alter PBPs

Answer 9

New gene (ex mecA in Staph)
Mutations/homologous DNA pieces creating mosaic PBPs (Strep and Neisseria)

Question 10

Vancomycin Resistance Mechanisms (2)

Answer 10

modifying target (D-ala D-ala changes)
Preventing Interaction

Question 11

VanA/VanB

Answer 11

Change from D-ala D-ala to D-ala D-lactate

Question 12

Staph Vanco Resistance

Answer 12

Thicker PG wall w/ less cross-linking exposes more binding sites for Vanco that do not interrupt cell wall synthesis.

Question 13

Quinolone Resistance Mechanisms (3)

Answer 13

Modifying Drug (rare)
Modifying target
Preventing drug-target interaction

Question 14

Modifying quinolone target

Answer 14

Mutations in the quinolone-resistance-determining region of topoisomerase IV/gyrase reduces binding affinity

Question 15

Mechanisms of Macrolide Resistance

Answer 15

Modifying Drug (rare)
Modifying Target
Preventing Interaction (efflux)

Question 16

Modifying Macrolide Target

Answer 16

erm gene encodes ribosomal methylase. Erm is inducible by macrolides but also give clindamycin resistance.

Question 17

D-Test

Answer 17

Used to distinguish between efflux or erm-mediated resistance to macrolide or clindamycin

Question 18

Aminoglycoside Resistance Mechanisms (3)

Answer 18

Modifying Drug (common; 3 major enymes)
Modifying Target (common)
Preventing interaction

Question 19

3 enzymes of AG modification

Answer 19

N-acetylation
O-nucleotidylation
O-phosphorylation