antbiotics Flashcards
types of cell wall synthesis inhibitors
beta-lactam antibiotics, cephalosporins, other drugs
types of protein synthesis inhibitors
tetracyclines, macrocodes and other drugs
types of folic acid synthesis inhibitors
sulfonamides, trimethoprim
Types of DNA synthesis inhibitors
quinolones
principles of antibiotic therapy
harm the parasite and not the host, mechanism of action affects processes unique to bacteria, processes common to bacteria and the host cell (more affinity for bacteria), type of bacteria (gram +, gram -, anaerobic, aerobic)
beta-lactam antibiotics (penicillin) characteristics
unstable in acidic pH and susceptible to destruction by beta-lactamase (when antibiotic is killed there is a risk of super infection), inhibit bacterial growth by impeding cell wall synthesis
super infection
caused by the antibiotic being killed, bacteria multiply out of control causing major infection and diarrhea
what does penicillin treat
streptococcous, meningococcous, anthrax, clostridium etc
penicillin side effects
non-toxic, serious effect due to hypersensitivity (anaphylactic shock), diarrhea (superinfection), yeast infection, resistance (90% of staph are beta-lactamase producers)
types of semi-synthetic penecilin
ampicillin, amoxicillin, methicillin
drug therapy guidelines
importance of correct doses, important to take the dose at correct time because drugs are only effective if there are enough in the blood
beta-lactam antibiotics (cephalosporins)
similar to penicillin (chemically, mechanism of action and toxicity), more stable to bacterial beat-lactamase, may cross blood-brain barrier, can be used in cases of penicillin sensitivity but are also sensitizing, given PO/IM/IV
what creates triple antibiotic therapy
bacitracin, polymyxin and neomycin
tetracycline characteristics
broad spectrum, accumulates inside the bacterial cell, binds to ribosomes, impeding formation of new protein, chelates calcium and other divalent cations, given PO or IV,
What type of horses should not have tetracyclines
young horses or pregnant mares because it binds to calcium,all drugs are only effective if they are free in the blood stream. oxytetracycline may be given to foals with contracted tendons so the calcium becomes bound and the tendons relax
macrolides
prevent bacterial protein synthesis, examples are erythromycin, clarithromycin, azythromycin, erythromycin is used in conjunction with rimfampin to treat pneumonia in foals, may cause diarrhea and light sensitivity (foals need ti be kept inside), fever, can be fatal in adult horses. used in young horses being treated for lawsonia
other protein synthesis inhibitors
aminiglycosides: streptomycin, neomycin, gentamycin (only given IV by vet), amikacin and trobramycin. used against enteric bacteria, extremely ototoxic (damage hearing) and nephrotoxic (damage kidney. Not very used in horses except in ointments
sulfonamide characteristics
some microbes need extracellular PABA to form folic acid. sulfas are structurally similar to PABA (so bacteria grab sulfa instead of PABA), sulfa reversibly blocks folic acid synthesis, bacteriostatic, not very used by itself anymore
trimethoprim
generally used in conjunction with sulfamethoxazole (SMZ), works with sulfa to give a stronger reaction (synergism), sulfa and trimethoprim together are bactericidal
how many antibacterials are generally given at one time?
one so they don’t prevent each other from working, which may cause endotoxemia
fluoroquinolones (floxacins)
newest antibiotic, broad spectrum, generally the last drug to be used tp help prevent resistance and killing the normal flora of the horse, have great activity against gram -, useful against e. coli
