Mechanisms of Antimicrobial Action and Resistance 1

Question 0

PBP 1a and 1b, what is their activity and function?

Answer 0

Transpeptidase activity

Peptidoglycan synthesis and cell wall elongation

Question 1

Molecular weight of Penicillin Binding Proteins goes ______ as the number increases (i.e. PBP 1a vs PBP 6)

Answer 1

Molecular weight is inversely proportional to the PBP #

Question 2

PBP 2 activity and function?

Answer 2

Transpeptidase activity

Maintains rod shape

Question 3

PBP 3 activity and function?

Answer 3

Transpeptidase activity

Peptidoglycan synthesis and septum formation

Question 4

PBP 4, 5, and 6 activity and function

Answer 4

D-alanine carboxypeptidase activity

Control extent of cross-links

Question 5

Are beta-lactams toxic to humans?

Answer 5

Targets of beta-lactams are uniquely bacterial so they are selectively toxic

Question 6

What is superinfection and why does it occur?

Answer 6

Overgrowth in large intestine with clostridium difficile (pseudomembranous colitits)
Its a nonspecific side effect of beta-lactams

Question 7

Hypersensitivity is a serious problem in response to what?

Answer 7

Beta-lactams

Question 8

When does haptene formation occur?

Answer 8

Reaction of beta-lactams with serum proteins

Question 9

Which group of bacteria are still highly sensitive to beta-lactams/penicillin G?

Answer 9

Group A streptococcus (beta-hemolytic)

Question 10

What is the largest mechanism of resistance to beta-lactams/penicillin G?

Answer 10

beta-lactamases

Question 11

Beta-lactamases of staphylococci act primarily as what?

Answer 11

Penicillinases

Question 12

The inoculum size has a large effect on what?

Answer 12

The MIC

Question 13

What are 3 limitations of early penicillins?

Answer 13

No oral administration
Resistant important groups of pathogens
Narrow antibacterial spectrum

Question 14

What happens if penicillin G is taken orally? What have we done to compensate for this?

Answer 14

Hydrolyzed by acid in the stomach

Give a much larger dose

Question 15

Which penicillin is acid-stable? How is it made?

Answer 15

Penicillin V

Made by adding phenoxyacetic acid to medium of mold producing penicillin

Question 20

Methicillin is _________ to beta-lactamase hydrolysis

Answer 20

refractory/resistant (?)

Question 21

Penicillin G can’t pass through what of which gram bacteria?

Answer 21

Outer membrane of gram negative bacteria

Question 22

What can pass through the outer membrane of gram negative bacteria due to its charged amino group? Is it acid-stable?

Answer 22

Ampicillin

Yes, ampicillin is acid stable

Question 23

Are there broad spectrum beta-lactamase refractory penicillins? What is the solution

Answer 23

No, so we add a broad spectrum penicillin with a beta-lactamase inhibitor

Question 24

Is methicillin refractory to beta-lactamases?

Answer 24

Yes, because if its large side chains… but that means that it also can’t cross the outer membrane of gram negative bacteria

Question 25

What are two active site directed inhibitors of beta-lactamases?

Answer 25

Clavulanic acid Sulbactam

Question 26

Methicillin resistant staph aureus: what is the resistance carried on? Is it intrinsic?

Answer 26

Yes, it is intrinsically carried on a transposon, meaning it is easily transmitted to other bacteria

Question 27

What is a haptene?

Answer 27

Antibiotic + serum protein that can cause formation of antibodies

Question 28

1st generation cephalosporin?

Answer 28

Cefazolin - antibacterial spectra and potency like penicillins

Question 29

2nd generation cephalosporin?

Answer 29

Cefoxitin - more potent and better against gram negatives (than cefazolin, 1st gen)

Question 30

What percent of people that are hypersensitive to penicillins are also hypersensitive to cephalosporins?

Answer 30

8%

Question 31

Are haptenes more commonly formed by penicillins or cephalosporins?

Answer 31

Penicillins (drug plus serum protein)

Question 32

Can bacteria have more than one beta-lactamase? Can they be effective against penicillins or cephalosporins?

Answer 32

Yes they can have more than one | Beta-lactamases can be effective against both penicillins and cephalosporins

Question 33

What is an advantage of carbapenems?

Answer 33

Resistant to many beta-lactamases

Question 34

Which bacteria can produce carbapenemases?

Answer 34

Enterobacteria

Question 35

What are 2 bacterial mechanism of resistance against carbapenems?

Answer 35

Active transport out of cell | Porin mutations preventing influx

Question 36

3rd generation cephalosporins?

Answer 36

Cefotaxime, Ceftazidime - even more potent (than 1st and 2nd gen) and highly effective against gram negatives but at the expense of being less effective against gram positives

Question 37

4th generation cephalosporins?

Answer 37

Cefepime - enhanced activity against gram negatives without loss of potency for gram positives

Question 38

5th generation cephalosporins?

Answer 38

Ceftaroline, Ceftobiprole - effective against MRSA and psuedomonas

Question 39

What percent of the population are hypersensitive to cephalosporins?

Answer 39

2%