Antibiotics in Food Animals Flashcards
Sulfonamides are time/concentration dependent
time dependent
sulfonamides are effective against ______
gram (+), gram (-) and some protozoa
organisms known to be resistant to sulfonamides
Pseudomonas, Bacteroides, and Enterococcus
T/F sulfonamides are bacteriostatic except potentiated sulfas which are bactericidal
True
additives increase strenght/effectiveness (i.e TMS)
where are sulfonamides distributed
wide distribution
joints via synovial fluid, CNS, prostate, urine etc - esp potentiated
T/F sulfonamides can be given to dairy cattle
False!
only sulfadimethoxine
T/F potentiated sulfas are used off label in calves and pigs
true
beta-lactams are time/concentration dependent
time dependent
beta lactams are bactericidal/static
bactericidal
what are some examples of beta lactams
penicillins and cephalosporins
what is the action of beta-lactams
bind penicillin-binding proteins
PBP-1 (panems) cause immediate cell lysis
T/F beta-lactams can be combines with a bacteristatic to increase efficacy
False!
Bacteria has to have 1 replication cycle for the beta-lactams to be cidal, combining with -statics make them useless
T/F penicillins generally need more time than cephalosporins
False
cephalosporins generally need more time than penicillins
______ require more exposure than ______
gram (-) require more exposure than gram (+)
how to organisms become resistant/avoid beta-lactams
production of beta-lactamase or alter PBP to prevent binding
3rd Generation Cephalosporins are usually unaffected by beta-lactamases
what is the spectrum of natural penecillins
gram (+), anaerobes, select gram (-): Listeria; and spirochetes
spectrum of aminopenicillins
more gram (-), some stains of E. coli and Salmonella
how does the spectrum of Cephalosporins differ from penicillins
similar but more gram (-) coverage as generation increases
T/F beta lactams have poor intracellular activity
True
what are some indications for tetracyclines
Anaplasma
wooden tongue (Actinobacillus)
lumpy jaw (Actinomycosis)
tetracyclines are ______ dependent
AUC/MIC dependent
AUC has to be about 120x MIC to be effective
what is the mechanism of tetracyclines
bind to 30s ribosomes, prevents protein synthesis
minimal affinity for mammalian ribosomes
routes of administration of tetracyclines
IV, IM, SQ, PO
poor ora absorption - except doxy
distribution of tetracycline
lipophillic (intracellular)
wide distribution (most tissues)
accumulate intracellularly, even leukocytes - posible anti-inflammatory effects
how are tetracycline eliminated
60% via glomerular filtration
40% through feces
there is increasing concern about ________ with tetracyclines
RESISTANCE!
examples of aminoglycosides
neomycin and gentamicin
aminoglycocides are bacteristatic/cidal and are concentration/time dependent
bactericidal
concentration dependent
aminoglycoside spectrum
primarily aerobic
gram (-)
T/F aminoglycosides and tetracyclines are both lipid soluble and act on the 30s ribosome
False!
aminoglycosides are highly water soluble and poorly lipid soluble
what is meant by post antibiotic effect see with aminoglycocides
accumulate in lysosomes and mitochondria
PAE - having effect in the desired area but no longer found in plasma at significant concentrations
why is there a long withdrawel period with aminoglycosides
chemically attracted to phospholipids
what toxicities are seen with aminoglycosides
nephrotoxic
ototoxic
these tissues have more phosphatidylinositol in their membranes than other body tissues (mainly gentamicin), this is also there is a concern about residue (kidney)
T/F gentamicin is recommended for use in cattle
FALSE!
not labeled for cattle! Aminoglycosides are a zero tolerance drugs!
what is the current withdrawel time for gentamicin in cattle
18 months per single injection for meat
5 days for milk following IV, IM or SQ
practictioners are stongly urged to refrain from using aminoglycosides in food animals except ______
neonatal pigs
what is thought to prevent bacterial inactivation of Florfenicol
fluorine at the 3’ carbon position
T/F florenfenicol is always bacteriostatic by nature
False
- blocks 50s ribsome, time dependent = static*
- at peak concentrations = cidal; always cidal for Fusabacterium necroforum*
spectrum for florfenicol
broad gram (-) → espcially BRD pathogens
some gram (+)
indications for florfenicol
BRD
keratoconjunctivitis
bovine interdigital phlegmon (aka foot rot)
distribution of florfenicol
lipid soluble, wide tissue distribution
concentrates in tear film (pinkeye)
CNS - H. somni (above MIC for 20hrs)
diseased lung
high urine concentrates
mammary (mastitis)
is extra-label use of florfenicol permitted
yes
- prolonged withdrawal for different than labeled production class*
- (ex. IM dose in lactating dairy cow has 60 day withdrawal)*
examples of macrolides
Azalides = Azithromycin, Tulathromycin, Gamithromycin, and Tildipirosin
spectrum of macrolides
fairly broad
gram (+)
select gram (-) → BRD pathogens
Azalides have activity against ________
mycoplasma
MOA of macrolides
inhibit protein synthesis by binding at 50s ribosomal subunit
why is there a possible antagonistic effect between macrolides and florfenicol
binding sites are close to each other
T/F tissue concentrations of macrolides are higher than serum concentrations
True
concentrate in cells more acidic than plasma, accumulate in lysosomes of leukocytes
macrolides have good absorption through ______
the gut
lincosamides are primarily used in ______
swine
avoid in hindgut and foregut fermenters- clostridial overgrowth
MOA of lincosamides
inhibit protein synthesis by binding 50s ribosome
lincosamides have essentially the same spectrum of activity as _____
macrolides
lincosamides are used to treat
Mycoplasma pneumonia
bacterial arthritis caused by Strep, Erysipelothrix, or Mycoplasma
what common adverse effect is seen with lincosamides
swelling of the anus
what is a highly restricted class of antibiotic that ELDU is strictly forbidden with
fluoroguinolones
enrofloxacin is approved for use in _______
cattle
swine
fluoroquinolones are bacteriostatic/cidal and time/concentration dependent
bactericidal
concentration dependent
spectrum of fluoroquinolones
most gram (-)
gram (+) variable susceptibilty - have higher MIC than gram (-)
MOA of fluoroguinolones
Inhibit bacterial DNA replication & transcription by binding the A subunit of DNA gyrase
like beta-lactams, fluoroquinolones should not be paired with a bacteriostatic anitbiotic
False
kill bacteria whether they are replicating or not
distribution of fluoroquinolones
wide
lipid soluble
what is the concern with use of fluoroquinolones in food animals
concern about transfer of resistance from animals to people
what are the bacteria of concern with fluoroquinolones
campylobacter
salmonella typhimurium type DT-104
