Antimicrobials 2

Question 1

MOA of sulfonamides?

Answer 1

folic acid synthesis inhibitors, folic acid is needed for DNA replication, so without it the bacteria stop growing and replicating. Doesn’t kill them. For this reason, the are bacteriostatic

Question 2

what kind of drug is prontosil and why doesn’t it kill bacteria in a test tube?

Answer 2

it was the first commercially available sulfonamide/antimicrobial, and it is a pro drug and must be metabolized in order to have an effect

Question 3

sulfonamides are good against what bacteria? general charactieristics of these drugs?

Answer 3

• bacteriostatic, time dependent
• good against:
• not good against: anaerobes
• not good for abscessation

Question 4

sulfonamides are readily absorbed by the GI tract in all species except: ______. How good is this drug at penetrating tissues?

Answer 4

ruminants
good at penetrating into tissues, will penetrate CNS and prostate, liver, kidney, lung

Question 5

sulfonamides are metabolized by ____ and eliminated by ____

Answer 5

liver, kidney

Question 6

the main use of sulfonamide drugs alone is

Answer 6

as oral product for production animals, common cause of drug residues, usually in pork

Question 7

what is a potentiated sulfonamide?

Answer 7

a sulfonamide used in combination with diaminopyrimidines for better antimicrobial activity.

sulfonamide + diaminopyrimidine=potentiated sulfonamide

Question 8

MOA of diaminopyrimidines?

Answer 8

inhibit folic acid synthesis, just via a different enzyme than sulfonamides

Question 9

what is the main PK difference between sulfonamides and diaminopyrimidines?

Answer 9

diaminopyrimidines can penetrate cell membranes and sulfonamides usually stay in extracellular space

Question 10

list some general characteristic for potentiated sulfonamides

Answer 10

• bacteriacidal (unlike sulfonamides which are bacteriostatic)
• time dependent (just like sulfonamides)
• not great for abscesses
• can penetrate prostate and CNS

Question 11

what kind of drug is trimethoprim/sulfadiazine? what bacteria is it good against?

Answer 11

a sulfonamide
- good against: strep, enterococcus, respiratory gram negs

Question 12

what are some adverse effects of trimethoprim/sulfadiazine?

Answer 12

• KCS in dogs
• hypothyroidism in dogs
• drool in cats
• diarrhea in horses

Question 13

what are some clinical uses of trimethoprim/sulfadiazine?

Answer 13

• resp infection in horses
• UTIs and resp in dogs
• skin wounds/bite wounds

Question 14

What are the two common categories of beta lactams used in vet med? MOA of beta-lactams?

Answer 14

• penicillins and cephalosporins
• beta lactams bind to penicillin binding proteins in the bacterial cell wall, permemently inactivating them and prevents cross linking of peptidoglycans in the cell wall. Without a functional cell wall, the bacteria undergo osmotic rupture

Question 15

beta lactams are most effective against what kind of bacterial population?

Answer 15

one that is growing!

Question 16

what kind of bacteria are beta lactams good for?

Answer 16

• good for gram +
• not as good for gram -, as it is more difficult to reach the penicillin binding proteins due to the outer cell membrane in gram -‘s

Question 17

why do beta lactams have very few adverse effects?

Answer 17

because mammals dont have cell walls

Question 18

what are some general PD and PK characteristics of beta lactams?

Answer 18

• bactericidal
• time dependent
• excreted largely by the kidneys–>can use for bladder infections

Question 19

what is the post antibiotic effect?

Answer 19

period of time after the drug concentration falls below the MIC during which bacterial growth is still inhibited

Question 20

for beta lactams, is there a post antibiotic effect?

Answer 20

yes (they are bactericidal), but ONLY for gram +

Question 21

resistance to beta lactams is common. how do bacteria accomplish this?

Answer 21

• beta lactamase production
• efflux proteins to reduce penetration
• penicillin binding proteins that resist binding by the drug

Question 22

true or false: you should not use penicillins with a bacteriostatic drug

Answer 22

true, since they work best in growing populations of bacteria we dont want to limit growth

Question 23

what kind of drug is penicillin G, what kind of bacteria is it good against?

Answer 23

beta lactam
good against gram +s, many anaerobes both gram + and -, spirochetes
not good against gram neg aerobes like E coli
suseptible to beta lactamase degradation

Question 24

list some different forms of penicillin G and how it’s given, etc

Answer 24

• penicillin G potassum or sdium: IV short acting
• procaine penicillin: IM, intermediate acting
• benzathine penicillin G: IM only, longer acting but less effective

Question 25

what happens if you give procaine penicillin G IV accidentally?

Answer 25

it can cause massive vasodilation and CNS toxicity

Question 26

what are the two aminopenicillins I need to know?

Answer 26

amoxicillin (PO) and ampicillin (IV)

Question 27

aminopenicillins are active against the same bacteria as penicillin G, except…

Answer 27

better at penetrating the gram - cell membrane ( E coli, proteus, salmonella)

Question 28

true or false: DO NOT give penicillins to hindgut fermenters

Answer 28

true! it causes disruptions to critical GI microbial populations which can lead to clostridia overgrowth!

Question 29

what bacteria are aminopenicillins good for?

Answer 29

honestly it covers most things in the little four square box model in the slides

Question 30

what is the penicillinase resistant penicillin I have to know? what is it good against?

Answer 30

cloxacillin
good for staphs, especially in mastitis

Question 31

if culture and sensitivity shows resistance to penicillinase resistant penicillins then…

Answer 31

you have a methicillin resistant staph (MRSA) and you cannot use beta lactam drugs

Question 32

what is a potentiated penicillin? what bacteria does it cover?

Answer 32

a beta lactamase inhibitor + penicillin, usually clavulanic acid and amoxicillin together. it covers literally everything except peusodmonas

Question 33

______ is the only beta lactamase inhibitor that is abdorbed orally

Answer 33

clavulanic acid