Beta Lactam Antibiotics

Question 1

Specifically, what enzyme do beta lactams block?

Answer 1

Block transpeptidase to prevent cell wall synthesis

Question 2

3 mechanisms of bacterial resistance against beta lactam antibiotics

Answer 2

1. Production of beta lactamases
2. Alteration in structure of PBPs (like in MRSA) leading to lower binding affinity
3. Alteration of outer membrane porins leading to decreased penetration

Question 3

Natural Penicillins

Answer 3

Penicillin G
Benzathine penicillin G (IM, long acting)
Procaine penicillin G (IM)
Penicillin VK (oral)

Question 4

Organisms susceptible to penicillin G or penicillin VK

Answer 4

Group streptococci
Viridians streptococci
Neisseria spp
Clostridium spp
Treponema pallidum

Question 5

Pencillinase Resistant Penicillins

Answer 5

Nafcillin
Oxacillin
Methicillin
Dicloxacillin

Question 6

What are penicillinase resistant penicillins used against?

Answer 6

MSSA

Question 7

Aminopenicillins

Answer 7

Ampicillin (parenteral) and Amoxicillin (oral)

Question 8

What are aminopenicillins developed for?

Answer 8

Increased activity against Gram negative aerobes

Question 9

What are aminopenicillins good to use against?

Answer 9

Gram Negative
Proteus mirabilis
Some E coli
Salmonella
Shigella
BL- H. influenzae

Gram Positive
Enterococcus spp.
Listeria monocytogenes (!!!)

Question 10

Carboxypenicillins

Answer 10

Ticarcillin (parenteral)

Question 11

What were carboxypenicillins developed for?

Answer 11

Further increased Gram Negative activity

Question 12

What are carboxypenicillins good against?

Answer 12

Pseudomonas aeruginosa

Question 13

Ureidopenicillins

Answer 13

Piperacillin (parenteral)

Question 14

Ureidopenicillins developed for?

Answer 14

Improved Gram positive activity while maintaining the strong Gram negative activity of carboxypenicillins

Question 15

Ureidopenicillins used against?

Answer 15

Pseudomonas aeruginosa
Enterobacter spp.
Serratia marcescens
Some Klebsiella spp.

Good activity against anaerobes

Question 16

Beta Lactamase inhibitors

Answer 16

Inhibit bacterial beta-lactamase
Often used in combination with antibiotics

Unasyn = ampicillin-sulbactam
Timentin = Ticarcillin-clavulanate
Zosyn = Piperacillin-tazobactam
Augmentin = Amoxicillin-clavulanate

Question 17

What are beta lactamase inhibitor combos good against?

Answer 17

Staph aureus
Bacteroides spp.
Haemophilus influenzae
Moraxella catarrhalis

Unasyn, Zosyn, Timentin good for polymicrobial infections