Pharmacology Exam 3 - Antimicrobials

What is an antimicrobial?

A drug that kills or inhibits the growth of microorganisms like bacteria, Protozoan, viruses, and fungi.

What is an antibiotic?

A specific category of antimicrobial that originates from one microorganism and suppresses the growth of another. Today, most antibiotics are synthetically made.

-cidal

kills the microorganism (e.g., bactericidal).

-static

inhibits the replication/growth of the microorganism (e.g., bacteriostatic).

Goal of antimicrobial therapy

Kill or disable pathogens without harming the host animal

Requirements of antimicrobial therapy

Pathogen susceptibility, high drug concentration at the infection site, and animal tolerance to the drug.

Sensitivity/Susceptibility in bacterial strains

Culture and MIC testing can determine the appropriate drug

What is antimicrobial resistance?

The ability of bacteria and other microorganisms to survive the effects of antimicrobial drugs.

Caused by misuse of antibiotics, leading to “superbugs.”

What are drug residues?

Presence of drugs or metabolites in animal tissues or food products.

Antimicrobial residues are not removed by cooking or pasteurization and can lead to allergic reactions or contribute to resistance in humans.

Penicillins. Gram positive. Not for eye, brain, or prostate. Excreted by kidneys. Watch for hypersensitivity reactions, especially with repeat exposure. Not IV if suspension. Give with food if GI upset. MRSA = resistant to all penicillins.

penicillin, ampicillin, amoxicillin, methicillin

Cephalosporins. 1st gen = gram positive, 3rd gen = gran negative. SQ long-acting (4-14d). Lower hypersensitivity than penicillins. GI upset possible. Really excreted.

cefovecin (Convenia), cefazolin, cephalexin

Aminoglycosides. Serious aerobic gram negative infections. Not well absorbed orally; great via nebulizer. Nephrotic and ototoxic-limit use duration. Don’t apply topically to dirty wounds. Absorbed through broken skin.

gentamicin, amikacin, tobramycin, neomycin

Fluoroquinolones. Broad spectrum. No ELDU in any food animal. Effective in reptiles for skin, respiratory, urinary infections. Can damage joint cartilage-avoid in growing animals. MRSA may resist via efflux pump.

enrofloxacin, marbofloxacin, orbifloxacin, pradofloxacin

Tetracyclines. Great for tick-borne and atypical bacteria. Hepatic excretion = OK in kidney disease. Causes tooth staining. Give water chaser-can cause esophageal damage. Slow/diluted IV-cardiac risk if rapid.

doxycycline, minocycline

Sulfonamides. Broad spectrum and protozoan. Enteric vs systemic forms. Can cause KCS, blood cell suppression. Dobermans = more prone to hypersensitivity.

sulfadimethoxine, sulfamethoxazole, sulfasalazine

Lincosamides. Used in “pulse therapy’ for periodontal disease. Contraindicated in hindgut fermenters-can disrupt flora.

clindamycin

Marcolides. Gram-positive respiratory. Chronic diarrhea (ELDU). Fatal arrhythmias possible if misinjected-handle carefully.

erythromycin, azithromycin, tylosin, tilmicosin (Micotil)

Antibacterial and antiprotozoal. Risk of resistance (Giardia). Neuro signs in high/prolonged doses (head tilt, tremors, ataxia).

metronidazole

Reaches hard-to-penetrate sites (brain, eye, prostate). Aplastic anemia risk in humans = handle with care. Safer, approved for cattle.

chloramphenicol, florfenicol

Antifungals. FDA-approved for systemic use for superficial infections. Common for ringworm.

ketoconazole, itraconazole, miconazole