title: The effect of growth-promoting antibiotics on the faecal enterococci of healthy young chickens.
abstract: Small groups of chickens were given feed containing either avoparcin, nitrovin, virginiamycin or zinc bacitracin from the day of their purchase as day-olds. Differences between the birds receiving growth promoters and the untreated controls were observed during the last third of the 23 d survey period. The enterococcal population of the 'dosed' birds contained a greater proportion of Enterococcus faecium than did that of the control birds while the converse was true for Ent. gallinarum. This apparent selection of Ent. faecium by the growth-promoting antibiotics had an influence on the incidence of resistance to therapeutic antibiotics among the enterococcal population as a whole. This was because this species was generally more resistant than Ent. gallinarum to cephalothin, the MLS antibiotics (erythromycin, lincomycin and tylosin) and tetracycline.
mesh_terms: D000821:Animal Feed; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000494:pharmacology; D001414:Bacitracin / Q000008:administration & dosage / Q000494:pharmacology; D002645:Chickens / Q000382:microbiology*; D004352:Drug Resistance, Microbial; D013293:Enterococcus faecalis / Q000187:drug effects / Q000302:isolation & purification; D005243:Feces / Q000382:microbiology*; D006020:Glycopeptides / Q000008:administration & dosage / Q000494:pharmacology; D009610:Nitrovin / Q000008:administration & dosage / Q000494:pharmacology; D013291:Streptococcus / Q000187:drug effects / Q000302:isolation & purification*; D014769:Virginiamycin / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D006020:Glycopeptides; D014769:Virginiamycin; D001414:Bacitracin; D009610:Nitrovin; C016249:avoparcin