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LAM II > Antibiotics in Food Animals > Flashcards

Antibiotics in Food Animals Flashcards

Fuselier material

1
Q

What 3 major spp.of bacteria have known resistance to sulfonamides?

A

Pseudomonas
Bacteroides
Enterococcus

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2
Q

Microbes that rely on follic acid will have susceptibility to this antibiotic…

A

sulfonamides

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3
Q

General concept behind sulfonamide activity…

A
  • In* bacteria that rely on FA:
  • FA** precursor —> {reductions*} —>THFA {bioavailable form}

Potentiating Sulfas…
PABA & dihydrofolate reductase are blocked —> prevents production of THFA
—> bactericidal activity

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4
Q

Why would we not use systemic sulfas to treat mastitis?

A

it’s a weak acid; milk is a weak base…

—> there’s some collection; but not enough to be therapeutic
but it still will be detected in milk

generally, don’t use it, esp not on dairies!

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5
Q

What is the only sulfonamide that you can use on adult dairy cows?

A

Sulfadimethoxine

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6
Q

T or F:
Potentiated sulfas are used off label in calves & pigs.

A

True

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7
Q

What do Penems bind to that causes immediate cell death?

A

Penicillin-Binding Protein-1

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8
Q

What binding site do all beta-lactams target?

A

Penicillin Binding Proteins
{PBP}

​Only _penems_ bind PBP-1
→ *immediate cell death

The others…*
{used in food animals: PBP-2, PBP-3}
cause cell membrane distortion so when the bacT goes to replicate, it can’t & it dies
…or it ruptures

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9
Q

T or F:

Penicillins always need more time than cephalosporins.

A

False!

Cephalosporins generally​ need more time than Penicillins.

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10
Q

What are the two main ways by which resistance or avoidance is achieved in the pathogen response to ß-lactams?

A
  • ß-lactamase production
  • altering ​the PBP​ to prevent binding
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11
Q 
What class of antibiotics could we use for **G+**​ ***anaerobic*** bacT,
*select* **G-** bacT {*_Listeria*_}, & spirochetes {_*Leptospirosa_*}?
A

Natural Penicillins
{Procaine Penicillin G}

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12
Q

In horses, the “shot gun approach” is penicillin & gentamicin, but we wouldn’t want that for calves because there’s an 18-month withdrawal period per injection of gentamicin. What did Dr. Fusilier tell us his favorite treatment for calf omphalophlebitis is? & Why?

A

Procaine Penicillin G & Ceftiofur
{strong G+ anaerobic; very good G- aerobic}

Bc it’s often a mixed infection…

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13
Q

What type of ß-lactams would we use to treat meningitis?

A

3rd Generation Cephalosporin
{i.e. Ceftiofur, Cefovecin (aka Convenia®)}

these 3rd gen.cephalosporins penetrate the CNS well

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14
Q

What’s Hexasol?

A

Combo: oxytetracycline & flunixine meglumine

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15
Q

What do tetracyclines work best for?

A

good for early stages of pink eye & foot rot,
​also works really well against Anaplasma!

bind 30s ribosome;
minimal affinity for mammalian ribosomes;
inhibit protein synth.

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16
Q

T or F:
No gentamicin is labeled for pigs older than 5 days old.

A

true

so if you give it to a month-old pig—> zero tolerance
{stays in kidney tissue for a long time}

17
Q

Gentamicin has an 18-month withdrawal period per injection in horses, but in piglets 3-5 days old, the withdrawal period is…?

A

40 days!

18
Q

Aminoglycosides {Neomycin, gentamicin} are bactericidal; this means the ___________ is what matters, not the __________.

A

Concentration, not the duration

becasue of this, the dosing frequency is increased to keep it at the right concentration

primarily G- aerobic spectrum

19
Q

What makes aminoglycosides dangerous from a toxicity standpoint?

A

They don’t differentiate b/t mammalian mitochondria & bacterial mitochondria

It just binds. This is also the reason we see phototoxicities & renal toxicities associated w.overuse of aminoglycosides.

20
Q

What are the restrictions regarding gentamicin and cattle?

A

NOT labeled for use in cattle!!

buuuut,
​current FARAD w.drawal times in cattle…
= 18 mo/single injection {meat}
& 5 days {milk}
…following IV, IM, or SQ dose

21
Q

What are the restrictions regarding gentamicin in goats & sheep?

A

18 mo/single injection {meat}
& 10 days {milk}

22
Q

What’s with food animals and chloramphenicol?

A

Chloramphenicol residues = lose license + go to jail

Florfenicol- took para-nitro group off — makes it safe

23
Q

most important properties of florfenicol {3}

A

bacteriostatic {by nature}*
binds 50s ribosome
time-dependent

*some pathogens have very lo MIC for florfenicol - so at its max concentration,
it’s so suppressive that it kills them…
i.e. bacteriocidal against Fusobacterium, and Manheimia & Pasteurella at its Cmax.

24
Q

In a case of BRD, keratoconjunctivitis, Histophilus somnei, or interdigital phlegmon {foot rot}, what antibiotic would we reach for?

A

Florfenicol

25
Q

A beef cow has mastitis that you’re not gonna be able to bring in & give intra-mammary infusions every day, but you can catch it about every 3rd day. What do you want to treat it with?

A

Florfenicol

systemic florfenicol has high concentrations in mammary tissue
& does really well for typical mastitis cases in beef cattle

26
Q

Florfenicol is not labeled for use in dairy cows, but extra-label use is permitted. What is the withdrawal period for florfenicol given IM in lactating dairy cattle?

A

60 days

If it was beef, it would be 28 days

27
Q

What is Tylosin mainly used for today?

A

Liver abscesses

some places use it for Mycoplasma, too

28
Q

What is the “parent compound” of the Macrolide class of antibiotics?

A

Erythromycin

29
Q

Where do macrolides accumulate?

A

in lysosomes of neutrophils & macrophages

30
Q

What are the Azalides?

A

newest development in the macrolide class; ​
have a higher positive charge—increasing affinity for intracellular sites

I.e. Azithromycin, Tulathromycin, Gamithromycin, & Tildipirosin

31
Q

Aminoglycosides as well as tetracyclines act by binding the 30s ribosome. So how are they different?

A

Tetracyclines bind reversibly;

Aminoglycosides bind irreversibly

32
Q

Does florfenicol concentrate better in healthy or diseased lung? What about macrolides??

A

Florfenicol:
better concentration in dz’d lungs
lipid soluble, concentrates in tear film, wide tissue distribution

Macrolides:
better concentration in healthy lungs

33
Q

Why do we like Pulmotil®?

A

tilmicosin {macrolide}
has good absorption thru the gut
also 72hr T1/2=healthy lung tissue

34
Q

What animals do we avoid using lincosamides?

A

Never use in fore-/hind-gut FERMENTORS…
BECAUSEthey have an affinity forG- organisms
—> Clostridial overgrowth —> diphtheric membranes

35
Q

Which fluoroquinolones are approved for cattle?

A

enrofloxacin
&
danofloxacin

LAM II (22 decks)

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