title: The effect of feeding diets containing permitted antibiotics on the faecal excretion of Salmonella typhimurium by experimentally infected chickens.
abstract: Groups of 45 chickens were fed continuously on diets containing 10 or 100 mg./kg. of different 'growth-promoting' antibiotics and infected orally with a nalidixic acid-resistant mutant of Salmonella typhimurium. The amount of S. typhimurium organisms excreted in their faeces was estimated by culturing them at weekly intervals and in a standard manner on plates of brilliant green agar containing sodium nalidixate, both direct and after enrichment in selenite broth. All of four groups fed diets containing 100 mg./kg. of nitrovin in three different experiments excreted much larger amounts of S. typhimurium than did groups fed antibiotic-free diets. In some, but not all, experiments, larger amounts were also excreted by groups fed diets containing 10 mg./kg. of nitrovin or 10 or 100 mg./kg. of flavomycin or tylosin. Feeding diets containing 10 or 100 mg./kg. of virginiamycin or bacitracin either did not influence or slightly increased the amount of S. typhimiurium excreted. Two groups fed continuously on diets containing 100 or 500 mg./kg. of sulphaquinoxaline for 44 days excreted smaller amounts of the S. typhimurium organisms that did groups fed antibiotic-free diets; no sulphonamide-resistant organisms of the S. typhimurium strain were isolated from the faeces.
mesh_terms: D000821:Animal Feed; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001414:Bacitracin / Q000494:pharmacology; D002645:Chickens; D004064:Digestive System / Q000382:microbiology; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000187:drug effects; D005243:Feces / Q000382:microbiology*; D005503:Food Additives; D007933:Leucomycins / Q000494:pharmacology; D009610:Nitrovin / Q000494:pharmacology; D012480:Salmonella Infections / Q000635:transmission; D012486:Salmonella typhimurium / Q000187:drug effects / Q000302:isolation & purification*; D013428:Sulfaquinoxaline / Q000494:pharmacology; D014769:Virginiamycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D005503:Food Additives; D007933:Leucomycins; D014769:Virginiamycin; D001414:Bacitracin; D009610:Nitrovin; D013428:Sulfaquinoxaline