Antibiotics In Food Animals Flashcards
What are the antibiotics available for use in food animals?
Sulfonamides
B- lactams
Tetracyclines
Florfenicol
Macrolides
Fluroroquinolones
Lincosamides (PIG ONLY)
Aminoglycosides — too long acting
What bacteria have known resistance against sulfonamides?
Pseudomonas, bacteriodies, and enterococcus
Are sulfonamides bacteriostatic/bactericidal?
Bacteriostatic, unless they are potentiated which are bactericidal
What is the MOA of sulfonamides?
Mimics PABA precursor at the beginning of the THFA pathway, blocking production of the active form of folic acid (THFA).
How are potentiated sulfas bactericidal?
Block both PABA and dihydrofolate reductatse
Where are sulfonamides distributed to?
Wide distribution
Joints via synovial fluid
CNS
Prostate
Urine
Weak acid —> low, non-theraputic concentration in milk but enough to test
What is the ONLY sulfonamide that can be used in adult dairy cows?
Sulfadimethoxine
Are B-lactams bacteriostatic or bactericidal ?
Bacteriocidal
MOA of B-lactams?
Bind to penicillin binding proteins
PBP-1 (penems)—> immediate cell lysis
PBP-2 and -3 (penicillins and cephalosporins) —> misshapen cell walls leading to rupture
What is the spectrum of penicillin?
Gram positive, anaerobes, select G- (listeria) and spirochetes
What is the spectrum of aminopenicillins?
Gram pos but more gram negs than penicillin
Some strains of E.coli and salmonella
What is the spectrum of activity fo cephalosporins?
Gram positive, anaerobes,
More gram negs as generation increases
What restrictions are in place for use of B lactams?
Follow label for aminopenicillin
ELDU is permitted as long as it follows AMDUCA is followed
PPG is currently used extra-label because label is outdated, contact FARAD for withdrawal times (40days in swine)
What is the mechanism of tetracyclines?
Binds the 30s ribosome to prevent protein synthesis
Are tetracyclines bacteriostatic or bactericidal?
Bacteriostatic and board spectrum
How are tetracyclines administered?
IV, IM, or SQ
Oral — all have poor oral absorption except doxycycline
What is the distribution of tetracyclines?
Lipophilic
Wide distribution — most tissues
Accumulate intracellularly, even leukocytes (anti-inflammatory effects)
How are tetracycline eliminated?
60% via glomerular filtration
40% via feces
If you are going to use an amino-glycoside, which should you pick for food animals?
Neomycin, gentamycin lasts too long in kidney
Are aminoglycosides bactericidal and bacteriostatic?
Bactericidal
Spectrum of aminoglycosides?
Primarily aerobic, gram negative
MOA of aminoglycosides ?
Irreversibly binds to the 30s ribosome —> cidal effect
Accumulates in lysosomes and mitochondria —> post-antibiotic effect
Attracted to phospholipids
What two toxicities can aminoglycosides cause?
Nephrotoxicity and ototoxicity
What are the restrictions for using aminoglycosides in food animas?
Try to refrain from use — lasts a long time in the kidney
Zero tolerance drugs
Gentamicin is NOT labelled for cows
Gent with drawl time 18months for single injection for meat and 5days for milk (sheep and goats 10 day milk withdrawal)
Piglets 1-3days old = 40day withdrawal
T/F: neomycin is approved for pre-ruminating calves or lactating cattle
False
What is the withdrawal time for oral administered neomycin in cows, swine, and goats?
1 day
2 days in sheep
T/F: chloramphenicol and florfenicol are both approved in food animals
FALSE
Florfenicol is approved
Chloramphenicol causes human aplastic anemia (contains a para-nitro group)
Spectrum of florfenicol?
Broad spectrum gram neg
Some gram pos
Indications for florfenicol?
BRD
Keratoconjunctivitis
Bovine interdigital phlegmon
MOA of florfenicol?
Inhibits protein synthesis by blocking peptidyltransferase activity at the 50s ribosomal subunit
What is the distribution of florfenicol?
Lipid soluble, wide tissue distribution
Concentrates in tear film
Achieves concentration in CNS above MIC for H. So nice for 20 hours
Good lung penetration
High urine concentration
High levels in mammary tissue
What restrictions exist for florfenicol use in food animals?
Extra-label use is permitted
Prolonged withdrawal for different than labeled production class
What antibiotic class has intracellular activity?
Macrolides
Azalides synthesized from erythromycin have a higher positive charge, increasing affinity for intracellular sites
What drugs are azalides?
Azithromycin
Tulathromycin
Gamithomycin
Tildipirosin
MOA of macrolides?
Inhibits protein binding at the 50s ribosomal subunits
Binding side is near florfenicol (can have antagonistic effect)
Spectrum of macrolides?
Broad
Gram pos and select frame neg
Mycoplasma
Distribution of macrolides?
Concentrate in cells that are more acidic than plasma
Good absorption through gut
Accumulate in lysosomes and leukocytes (neutrophils and macrophages)
Tissue concentration is higher than serum concentration
Tilmucosin can stay how long in healthy lung tissue?
72 hours
Tulathromycin has a half life of _______ in cattle lung and ________ in swine lung?
184hours, 140hours
What food animal can lincosamides be used in?
Swine
What does lincosamide cause in foregut and hindgut fermenters?
Clostridial overgrowth
MOA of lincosamide?
Inhibit 50s ribosome —> inhibit protein synthesis
What bacteria in lincosamide usually used for in swine?
Mycoplasma pneumonia
Bacterial arthritis — strep, erysipelohris, or mycoplasma
Common adverse effect of lincosamide ?
Swelling of the anus
What two fluoroquinolones are approved in cattle?
Enrofloxacin and danofloxacin
ELDU is FORBIDDEN
Spectrum of fluoroquinolones ?
Most gram neg
Gram positive are variable susceptible and have a higher MIC than gram neg
MOA of fluoroquinolones?
Inhibit DNA synthesis and transcription by binding A subunit of DNA gyrase
Distribution of fluoroquinolones ?
Lipid soluble, wide distribution
