Penicillins Flashcards
Which are betalactam antibiotics?
Penicillins, cephalosporines
Mode of action
Time dependent bactericidal, kill bacteria slow- a few days of treatment is needed!
Minimum duration 3-5 days.
PAE lengthens effect
Needs to be taken 2-3x/d to cover the whole day.
Mechanism of action: target
Affects the peptidoglycan layer- transpeptidase and carboxylase are the tagets -> to no transpeptide binding= cell wall inhibition -> bacterolysis.
Only active on dividing bacteria, existing cell wall has penicillin no effect on.
Resistance
Ab ovo- mycoplasma (no cell wall!)
Gram- has LPS- difficult to penetrate, so more resistant.
Gram- has porin channels that penicillin enters
PSEUDOMONAS ARE COMPLETELY RESISTANT!
Acid fast cell wall- mycobacterium.
Chlamydia, Brucella- no chance to penetrate.
Betalactamase!!! destroys betalactam ring!
Betalactamase production
Helps with resistance.
Gram+ Staphylococcus: outside cell wall.
Gram- all produce betalactamase- especially E.coli and Pseudomonas (completely resistant!!)
Betalactamase inhibitors:
Clavulenic acid, Tazobactam, Sulbactam
PBP-gene mutation
Staphylococcus changed its PBP-structure -> Methicillin resistance.
Spectrum ranges:
Narrow spectrum: Gram+
Penicillinase stable penicillins: Gram+ ONLY! Staphylococcus, Streptococcus
Broad spectrum: Gram+ and Gram- NOT PSEUDOMONAS.
Penicillins acting against pseudomonas, Gram+, Gram-
Narrow range penicillins: DRUG NAMES
Benzylpenicillin Na, K- water soluble. IV, IM
Benylpenicillin benzathine- don’t reach MIC on its own. Long duration.
Benzylpenicillin procaine- long duration.
Benzathine+ procaine often combined- reach MIC over several days. SC, IM
These 3 drugs has no oral absorption!
Phenoxymethyl penicillin- oral. Gram+ Cl. perf in poultry.
Narrow range penicillins: target, pharmacokinetics
Most Gram+, fastidious: haemophilus, histophilus, bibersteinia, pasteurella, mannheimia.
Absorption: Oral=Phenoxymethyl penicillin, IV, IM, SC, can’t reach IC.
Distribution: Bad/moderate. Can’t cross barriers.
Metabolism: Hydrophilic, minimal met. in the liver= safe in liver patients.
Excretion: Urine= good for UTI- Amoxicillin is the 1st choice.
Side effects of narrow range:
Allergy in humans, not common in animals.
Dysbacteriosis: horse and herbivore rodents- if diarrhea- stop treatment!
Most toxic: Benzylpenicillin procaine- ataxia, tremours, movemnet disorder, piglets are most senstive to it- they have no procainase.
Narrow range penicillins: Indications
Respiratory infection, swine erysipelas, anthrax, tetanus, necrotic enteritis, mastitis, metritis, streptococcosis= strangles, septicemia, mastitis, streptococcus suis, skin disease, sore throat.
Penicillinase stable penicillins:
ONLY Gram+, can’t be destoyed by betalactamase.
Main target: Staphylococcus, Streptococcus
Disease: Mastitis- cow
Acid sensitive: Methicillin
Acid resistant: Oxacillin, Cloxallin, Dicloxacillin, Flocloxacillin: best distribution, stays longer in mammary gland.
Broad spectrum:
Most Gram+, several gram-. E.coli, Salmonella, Klebsiella.
Proteus, fusobacterium, bacteroides: oral cavity, bite wounds, foot rot.
Amoxicillin, Ampicillin
Amoxicillin:
Broad spectrum Oral absorption: Good/ excellent With food: no change Salt: Amoxicillin Na, Amoxicillin trihydrate mixed in food Combo: Clavulenic acid
NOT ORAL TO HORSE!
Sensitive to betalactamase
Anthrax, erysipelas, tetanus, E.coli, GI- clostridium, dermatitis and soft tissue: Staphylococcus
UTI- amoxicillin alone- 100x more cc in urine than in plasma.
