Antimicrobials 2 Flashcards
MOA of sulfonamides?
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
what kind of drug is prontosil and why doesn’t it kill bacteria in a test tube?
it was the first commercially available sulfonamide/antimicrobial, and it is a pro drug and must be metabolized in order to have an effect
sulfonamides are good against what bacteria? general charactieristics of these drugs?
- bacteriostatic, time dependent
- good against:
- not good against: anaerobes
- not good for abscessation
sulfonamides are readily absorbed by the GI tract in all species except: ______. How good is this drug at penetrating tissues?
ruminants
good at penetrating into tissues, will penetrate CNS and prostate, liver, kidney, lung
sulfonamides are metabolized by ____ and eliminated by ____
liver, kidney
the main use of sulfonamide drugs alone is
as oral product for production animals, common cause of drug residues, usually in pork
what is a potentiated sulfonamide?
a sulfonamide used in combination with diaminopyrimidines for better antimicrobial activity.
sulfonamide + diaminopyrimidine=potentiated sulfonamide
MOA of diaminopyrimidines?
inhibit folic acid synthesis, just via a different enzyme than sulfonamides
what is the main PK difference between sulfonamides and diaminopyrimidines?
diaminopyrimidines can penetrate cell membranes and sulfonamides usually stay in extracellular space
list some general characteristic for potentiated sulfonamides
- bacteriacidal (unlike sulfonamides which are bacteriostatic)
- time dependent (just like sulfonamides)
- not great for abscesses
- can penetrate prostate and CNS
what kind of drug is trimethoprim/sulfadiazine? what bacteria is it good against?
a sulfonamide
- good against: strep, enterococcus, respiratory gram negs
what are some adverse effects of trimethoprim/sulfadiazine?
- KCS in dogs
- hypothyroidism in dogs
- drool in cats
- diarrhea in horses
what are some clinical uses of trimethoprim/sulfadiazine?
- resp infection in horses
- UTIs and resp in dogs
- skin wounds/bite wounds
What are the two common categories of beta lactams used in vet med? MOA of beta-lactams?
- 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
beta lactams are most effective against what kind of bacterial population?
one that is growing!
what kind of bacteria are beta lactams good for?
- 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
why do beta lactams have very few adverse effects?
because mammals dont have cell walls
what are some general PD and PK characteristics of beta lactams?
- bactericidal
- time dependent
- excreted largely by the kidneys–>can use for bladder infections
what is the post antibiotic effect?
period of time after the drug concentration falls below the MIC during which bacterial growth is still inhibited
for beta lactams, is there a post antibiotic effect?
yes (they are bactericidal), but ONLY for gram +
resistance to beta lactams is common. how do bacteria accomplish this?
- beta lactamase production
- efflux proteins to reduce penetration
- penicillin binding proteins that resist binding by the drug
true or false: you should not use penicillins with a bacteriostatic drug
true, since they work best in growing populations of bacteria we dont want to limit growth
what kind of drug is penicillin G, what kind of bacteria is it good against?
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
list some different forms of penicillin G and how it’s given, etc
- penicillin G potassum or sdium: IV short acting
- procaine penicillin: IM, intermediate acting
- benzathine penicillin G: IM only, longer acting but less effective
what happens if you give procaine penicillin G IV accidentally?
it can cause massive vasodilation and CNS toxicity
what are the two aminopenicillins I need to know?
amoxicillin (PO) and ampicillin (IV)
aminopenicillins are active against the same bacteria as penicillin G, except…
better at penetrating the gram - cell membrane ( E coli, proteus, salmonella)
true or false: DO NOT give penicillins to hindgut fermenters
true! it causes disruptions to critical GI microbial populations which can lead to clostridia overgrowth!
what bacteria are aminopenicillins good for?
honestly it covers most things in the little four square box model in the slides
what is the penicillinase resistant penicillin I have to know? what is it good against?
cloxacillin
good for staphs, especially in mastitis
if culture and sensitivity shows resistance to penicillinase resistant penicillins then…
you have a methicillin resistant staph (MRSA) and you cannot use beta lactam drugs
what is a potentiated penicillin? what bacteria does it cover?
a beta lactamase inhibitor + penicillin, usually clavulanic acid and amoxicillin together. it covers literally everything except peusodmonas
______ is the only beta lactamase inhibitor that is abdorbed orally
clavulanic acid
