Misc. Antibiotics

Question 1

Ionophores:

Answer 1

Anti-coccidial. Improved feed efficiency, weight gain, and milk production in cattle. Decrease bloat.

Question 2

How do ionophores work?

Answer 2

Bind sodium in the cell wall, leading to influx of H+ into cell. Lethal pH drop kills bacteria.

Question 3

How do ionophores work to increase weight gain/food efficiency?

Answer 3

Eliminates some Gram + bacteria in the gut, pushing production of VFAs towards proprionic acid and away from lactic acid, therefore increasing glucose production. Methane production is also decreased.

Question 4

Ionophores are contraindicated in:

Answer 4

Horses. NEVER USE IONOPHORES IN HORSES. Severe muscle damage, including the heart. Renal damage due to myoglobinuria.

Question 5

Spectinomycin:

Answer 5

Like an aminoglycoside, but lacking the toxicities. Water soluble, extracellular concentration. DOES NOT cross BBB. Mostly used in poultry and swine. NOT absorbed orally.

Question 6

How does spectinomycin work?

Answer 6

Bacteriostatic. Binds to 30S ribosomal subunit to inhibit protein synthesis.

Question 7

What does spectinomycin work on?

Answer 7

Related to aminoglycosides, so they do NOT work on strep and anaerobes. No special spectra, except mycoplasma.

Question 8

Avilamycin:

Answer 8

Works at the 50S ribosomal subunit of Gram + bacteria. Only used in pigs.

Question 9

Nitroimidazoles:

Answer 9

Does NOT work in an aerobic environment. Nitro group redux in anaerobic bacteria breaks DNA. Some antiprotozoal activity. BANNED IN FOOD ANIMALS.

Question 10

What are some adverse rxns of nitroimidazoles?

Answer 10

Neurologic disturbances, anorexia/vomiting, bone marrow suppression.

Question 11

Rifampin:

Answer 11

Human anti-tuberciosis drug. Maintains activity in purulent material. Crosses BBB. Bactericidal. NEVER USE ALONE.

Question 12

Isoniazid:

Answer 12

Activity only against actinomyces and mycobacteria. Can be fatally toxic in the dog.

Question 13

Nitrofurans:

Answer 13

Relatively broad spec. Suitable only for UTIs. Poor oral absorption.

Question 14

What are some adverse reactions to nitrofurans?

Answer 14

Nitrofurans are carcinogenic.

Question 15

Novobiocin:

Answer 15

Vet use only for Gram + pathogens, particularly Staph.

Question 16

Pleuromutilins:

Answer 16

Treatment for swine dysentery (Serpulina). Tiamulin and Carbadox. May be potential carcinogen.

Question 17

Bacitracin:

Answer 17

Used only topically or orally. Against Gram + bacteria (Corynebacteria, Staph, Strep, Clostridia, and some spirochetes). Part of “triple antibiotic” topicals. Orally used to treat swine dysentary.

Question 18

Polymyxin B:

Answer 18

Too nephrotoxic and neurotoxic for parenteral use. Part of triple antibiotic topicals. Can bind endotoxin.

Question 19

Mupirocin:

Answer 19

Topical use only for skin infections caused by Steph/Strep. Does NOT belong to many drug family.

Question 20

Silver sulfadiazine:

Answer 20

Disrupts cell membranes. Broad spec, including antipseudomonal activity. Used in wounds, burns, and otically.

Question 21

Methenamine:

Answer 21

Predates even sulfas. Prodrug used to treat UTIs. Require urinary acidification.

Question 22

Fosfomycin:

Answer 22

Inhibit cell wall production. Broad spec. Bactericidal.

Question 23

Vancomycin:

Answer 23

Used in MDR enterococcal and staph infections. BANNED in food animals.

Question 24

Streptogramins:

Answer 24

Used against Gram+ bacteria. Public health concern with resistance.

Question 25

Oxazolidones - Linezolid

Answer 25

Used against Gram + bacteria. Adverse rxns include: bone marrow suppression, peripheral neuropathy, lactic acidosis have been reported in humans. Expensive.