Antimicrobials: Resistance

Question 2

Prototypical Penicillins

Answer 2

ß lactamase carrying bugs, deep strep

Question 3

Extended Spectrum Penicillins

Answer 3

ß lactamase carrying bugs

Question 4

Penicillinase Resistant Penicillins

Answer 4

MRSA

Question 5

Anti-Pseuodomonal Penicillin

Answer 5

ß lactamase carrying bugs

Question 6

Vancomycin

Answer 6

S. Aureus - VRSA, Enterococcus - VRE. D-ala switch to D-lac. Pay back 2-Dalas for Vandalizing

Question 7

Macrolides

Answer 7

Methylation of 23S rNA binding site

Question 8

Lincomycin

Answer 8

S. Aureus: Erythromycin induced Clindamycin resistance

Question 9

Synthetic Agents

Answer 9

Plasmid encoded acetyltransferase that inactivates drug

Question 10

Tetracylines

Answer 10

Many gram (+) and Gram (-) are now resistant via decrease uptake or increased efflux from cell: plasmid encoded pumps

Question 11

Aminoglycosides

Answer 11

Transferase enzymes that inactivate the drug by acetylation, phosphorylation, or adenylation

Question 12

Fluoroquinolones

Answer 12

Cross resistance, increased efflux, decreased permeability to drugs, enzymatic mutations. 10% Campy in travelers diarrhea are resistant to Cipro

Question 13

Sulfonamides

Answer 13

Widespread resistance to sulfoamethoxazole alone, efflux, enzyme mutations, decrease in uptake, increase in PABA synthesis

Question 14

Nitrofurantoin

Answer 14

Proteus, pseudomonas, enterobacter, klebsiella are resistant, making it 2nd line for UTIs

Question 15

Antituberculuar Agents (Rifampin)

Answer 15

rpoB = point mutation in RNA polymerase. Emerges rapidly, esp if used alone.

Question 16

Antitubercular agents (Isoniazid)

Answer 16

katG = catalase (-) mutation (70-95% of strains). Also InhA alterations.