Antibiotics Flashcards
prophylactic Ab use
20-30min prior to incision (to prevent bacteria that were on the animals skin)
Killing pattern
time v. concentration dependent
Concentration dependent
concentrates in tissues, can give longer dosing intervals.
minimum concentration in SERUM to have effect… (Aminoglycosides(gentamycin&amikacin), Fluoroquinolones(enrofloxacin, Marbofloxacin), Metronidazole)
time dependent
serum concentration must stay above minimum bacteriacidal levels between dosing intervals
- w/o persistent effects: B lactams (penicillin, cephalosporin)
- w/ persistent effects: (Lincosamides(lincomycin), Macrolides(clindamycin, azithromycin, tylosin), Tetracyclines(oxytetraclin, doxycyclin)
time dependent
serum concentration must stay above minimum bacteriacidal levels between dosing intervals
- w/o persistent effects: B lactams (penicillin, cephalosporin)
- w/ persistent effects: (Lincosamides(clindamycin), Macrolides(azithromycin, tylosin), Tetracyclines(oxytetraclin, doxycyclin)
Beta Lactams
Penicillins, Cephalosporins
+,-,ana
Cell wall synthesis inhibitors
penicillin, cephalosporin, vancomycin
+,-,Ana
inhibition of protein synthesis (30 or 50s)
Chloramphenicol, tetracyclin, clindamycin
inhibition of protein synthesis (30s) Aminoglycosides
gentamycin, amikacin
inhibition of protein synthesis (30s) Aminoglycosides
gentamycin, amikacin
Aminoglycosides: G-
Antimetabolites
Trimethoprim, sulfonamides
Antimetabolites
Trimethoprim, sulfonamides
+,-
cystitis/UTI
mainly gram negative aerobes - clavamox
Large GI
E.coli and anaerobes in heavy numbers
Large GI
E.coli and anaerobes in heavy numbers
Gentamycin only good for e. coli, prefer 3rd generation cephalosporin
MIC
minimal inhibitory concentration
results of MIC
susceptible, intermediate sensitive, resistant
step 2 in MIC gives
minimal bacteriocidal concentrations
Metronidazole
Quinolones
tetracyclins
lyncosamides
Metronidazole - Ana
Quinolones - G-
tetracyclins - G+, some G-
lyncosamides - G+, Ana
What is the most important mechanism of bacterial resistance?
plasmids!
Food animal antibiotic use has the risk of
antibiotic resistant strains in the humans that eat the meat
- avoiding antibiotics for viral infections
- using culture/sensitivity
- using the correct dose/frequency/route
- avoiding using the newest abx
All help to do what?
Slow the resistance process
beta lactams are all
bacteriocidal
beta-lactam drugs
Penicillins, cephalosporins, monobactams and carabapenems
beta-lactams are widely used in vet med because
broad spectrum, favorable safety profiles, clinical efficacy
because beta-lactams are time dependent
they are eliminated quickly(short half life, lipophilic), need to be given more often to keep over minimum concentration needed.
because beta-lactams are time dependent
they are eliminated quickly(short half life, hydrophilic), need to be given more often to keep over minimum concentration needed.
As you go down the cephalosporin generations they become more bacteriacidal towards
gram negative and anaerobes
Patient with bacterial encephalitis/meningitis, do you want to use penincillin?
No, will penetrate enflamed BBB and cause seizures?
Beta-Lactams resistance, 3 mechanisms?
- production of beta-lactamase
- changes in structure of PBPs(MRSA) (giving plasmids to neighbors?)
- impenetrable membrane pores
Penicillin drug interactions
limited -> diminished renal tubular secretion (phenylbutazone, sulfonamides, salicylates, barbituates)
Penicillin drug interactions
limited -> diminished renal tubular secretion (phenylbutazone, sulfonamides, salicylates, barbituates) so it stays in the body longer?
Cephalosporins
similar to penicillins
most are NOT protein bound
if you’re resistant to penicillin common to be resistant to
chephalosporin
second generation cephalosporin
loses gram positive affect (wont kill staph, pseudomonas)
don’t use first.
Imipenem
used when nothing else is working, highly resistant cases(betalactamase bacteria with penicillin resistance). Use with anti-septic.
Polypeptides (3)
Bacitracin, vancomycin(very uncommonly used bc big gun), polymixin
-also cell wall inhibitors, used in eye drops for conjunctivitis
Very few agents are effective against intracellular organisms. _______ and _______ are.
Tetracyclin, Macrolides
Aminoglycosides (Gentamycin, Amikacin)
- concentration dependent
- use for G- anaerobes, inhibit protein synthesis 30s
- great for UTIs given animal doesn’t have renal failure.
Predominant organs for aminoglycoside toxicity
renal cortex, inner ear
erlichia, intracellular pathogen use
tetracyclines (tetracyclin, doxycycline)
tetracyclines
- bacteriostatic, inhibition protein synthesis 30s
- food reduces absorption orally
- caustic to esophagus (Causes stricture) if don’t follow pill with water in cats
Macrolides
effective against G+, -, and intracelular organisms (ricketsia and mycoplasma)
(some make clostridium sporylate, Clindamycin)
azithromycin
macrolide for respiratory disease
Chloramphenicol
bacteriostatic, inhibits protein synthesis 50s
**Never use in food animals
sulfonamides
- inhibits pyrimidine, DNA synthesis
- bacteriostatic
- G+/-, not psuedomonas
trimethoprim
potentiated agent sulfonamide
**when combined with sulfa’s become bacteriocidal b/c inhibits two sequential steps in pyrimidine synthesis
Fluoroquinolones/quinolones
Enrofloxacin, Marboflaxacin
- inhibits bacterial DNA gyrase
- concentration dependent (but lipophilic unlike penicillin so isn’t eliminated as quick)
- bacteriacidal
- accumulates in Mphages -> good for pulmonary infections
- broad spectrum for G- and aerobes
- This is not a first abx!
problems with quinolones
puppies affects chondrocytes, cats -> risk blindness
Metronidazole
- concentration dependent
- protozoa (giardia)
- Also is immune modulator
- most G- anaerobes (clostridium, fusobacterium) not G+ especially large bowel rupture/septicemia
Metronidazole pharmacokinetics
lipophilic, food increases bioavailability in dogs
UTI is an _____ infection
G- aerobic
adverse reactions of metronidazole
- metallic taste
- anorexia, vomiting, diarrhea
- neuro and hepatotoxic at high doses
Lincosamides:Clindamycin
most anaerobes (strep, staph) oropharyngeal or respiratory infections sometimes sepsis
Bypass the BBB***
Chloramphenicol, doxyclcline, metronidazole, some 3rd gen cephalosporins
Renal, Liver and biliary excretion
macrolides
hepatic excretion
doxy, phenicols, metrinidazole
Liver and Kidney Excretion
sulfas, quinolones
Rifampin
tx rhodococcus in horses
