Effect of growth promotant usage on enterococci species on a poultry farm.

The species population of enterococci isolated from four poultry houses for six grow-outs on one farm was determined. Two houses on the farm were control houses and did not use any antimicrobials, while two other houses on the farm used flavomycin, virginiamycin, and bacitracin during different poultry grow-outs. Litter, chick boxliners, feed, and poultry carcass rinses were obtained from each house and cultured for the presence of enterococci. Nine species of enterococci (Enterococcusfaecalis, E. faecium, E. avium, E. casselifiavus, E. cecorum, E. durans, E. gallinarum, E. hirae, and E. malodoratus) were identified from the study. Enterococcus faecalis was isolated more frequently from chick boxliners (n=176; 92%) and carcass rinses (n=491; 69%), whereas E. faecium was found more frequently in litter (n=361; 77%) and feed (n=67; 64%). Enterococcus faecalis (n=763; 52%) and E. faecium (n=578; 39%) were isolated most often from the farm and houses, regardless of antimicrobial treatment. Fifty-two percent of E. faecalis and 39% of E. faecium were isolated from both control (n=389 and 295, respectively) and treatment (n=374 and 283, respectively) samples. This study indicates that antimicrobial usage on this farm did not alter the resident population of enterococci.