VDPAM 4870 - Exam 3: Dairy and Beef

Alexander Fleming

penicillin, 1928; “mold inhibits bacteria”

antimicrobials

used against microorganisms; antifungals, antibiotics

sulfonamides

blocks folic acid synthesis, used for bacteria, coccidia; bacteriostatic; toxic to kidney if overdosed

beta-Lactam

penicillins, cephalosporins; block cell wall synthesis; bacteriocidal

tetracyclines

bind 30s ribosomal subunit interfering with bacterial messenger RNA; bacteriostatic, broad spectrum; significant resistance

aminoglycosides

irreversibly bond to 30s of bacterial ribosome; bacteriostatic, gram negative, narrow spectrum

chloramphenicols

synthetically manufactured, bacteriostatic - 50s subunit; first broad-spectrum atb

Macrolides

inhibits 50s subunit; bacteriostatic; significant resistance

Lincomysin

binds 50s subunit; bacteriostatic/cidal; absorbant in feed and water

Fluoroquinolones

inhibit bacterial DNA gyrase; bacteriocidal; narrow spectrum, gram negative; ex: Baytril

Routes of Administration

IV, IM, SQ, IP, oral

IV

immediate response, short duration, straight into circulation; ex: tail vein or auricular vein in cattle; jugular used in cattle and small ruminants

IM

longer duration, takes time to reach circulation, can cause muscle damage; given in triangle behind neck to avoid damaging retail cuts

SQ

similar to IM, longer duration, no muscle damage; ex: inject in “tent”

IP

rare; dangerous; flank approach

oral

ease: feed→water→individual; animal dosing: individual→water→feed

KIS test

kidney inhibition screening test

CHARM milk test

done on every tanker; esp. beta lactams

Antibiotics

treat, prevent, control; NOT for growth promotion

Intrinsic Resistance

ability of bacteria to resist activity of antimicrobial naturally; insensitivity

Acquired Resistance

organism has developed resistance to agent which was previously susceptible; genetic and mechanisticG

Genetic resistance

gene mutation, horizontal gene transfermec

mechanistic resistance

modification of antibiotic molecule; decreased antibiotic penetration and efflux; changes in target site

Horizontal Gene Transfer

transfer of DNA (usually a plasmid); transformation, transduction, conjugation

Transformation

incorporation of naked DNA; simplest

Transduction

virus infects bacteria; requires no physical contact betwee cells

Conjugation

cell-to-cell contact; majority of resistance in hospital environment; plasmids and transposons

Modification of antibiotic

chemical alteration via enzymes; destruction of antibiotic molecule

Decreased permeability

alteration of diffusion channels; decreased uptake

Increased Efflux

substrate-specific; broad specificity

Mastitis

Inflammation of mammary gland due to bacterial infection; most expensive dairy disease; est. cost ~ $100-500/case

Clinical Signs of Mastitis

abnormal milk, swollen quarter, visibly ill animalsub

Subclinical signs of mastitis

normal milk w/o signs of systemic illness; requires milk quality testing to identify; ~70-75% of cases

Clinical Mastitis

cow: painful quarter; fever, off feed; milk: chunky, flaky, bloody, yellow

Mastitis Organisms

contagious: cow-to-cow or milker-to-cow; environmental: bacteria naturally in environment

Main WBC that battles mastitis

neutrophils

Somatic Cell Count

expressed in cells per mL of milk; mastitic cows have HIGH levels in the millions

PMO requirement for bulk tank milk SCC

<750,000/mL

strep ag

lives in cisterns and ducts, not long outside of cow; subclinical or chronic infection; easy to treat

staph aureus

invades tissues of udder, can live outside cow; produces enzymes that resist antibiotics; subclinical or chronic infection, hard to treat

mycoplasma bovis

purchased into herd; acute clinical infection; no treatment (doesn’t have a cell wall)

environmental mastitis

coliforms; transmission through environment; usually acute and clinical; treatment focuses on supportive care

environmental streps

transmission through environment; acute clinical - self cure; treatment through IMM therapy

Mastitis testing

CMT, BTSCC, Milk cultures

CMT

California Mastitis test; lyses cell wall, thickens liquid as molecules bind together

BTSCC 

bulk tank somatic cell count; controls acceptance of abnormal milk into general milk supply; federal max = 750,000; good for herd testing, not for individuals

Milk Cultures

bulk, groups, and individuals; good for big picture bacteria identification

MacConkey

gram - selectiveBl

Blood agar

non-selective culture

Corkscrew claw

genetic; claws grow over/around each other; animal should not be bred

Signalment

age, sex, breed of patient