Submitted to: Avian Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/18/2005
Publication Date: 9/1/2005
Citation: Debnam, A.L., Jackson, C.R., Barrett, J.B., Hofacre, C.L. 2005. Effect of growth promotant usage on enterococci species on a poultry farm. Avian Diseases. 49(3):361-365. Interpretive Summary: Although the effect of growth promoting antimicrobials on antimicrobial susceptibility of enterococci from poultry has been previously reported, information is lacking on if and how the antimicrobials affect the species population of enterococci. In this study, the effect of three growth promoting antimicrobials (bacitracin, flavomycin, and virginiamycin) on the species population of enterococci from chick boxliners, litter, feed, and carcasses was determined. Enterococcus faecalis was isolated most often from chick boxliners and carcass rinses, while Enterococcus faecium was isolated more frequently from litter and feed than any other enterococcal species. Results from control and treated samples were comparable indicating that antimicrobial treatment did not alter the resident population of enterococci. This information will be useful for policy makers, researchers and consumers in order to understand the effects of growth promotant usage in poultry.
Technical Abstract: 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 (E. faecalis, E. faecium, E. avium, E. casseliflavus, 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 Enterococcus faecium (n=578; 39%), were isolated most often from the farm and houses regardless of antimicrobial treatment. Fifty-two percent of Enterococcus faecalis and 39% of Enterococcus faecium were isolated from both control (n=389 and 295, respectively) and treatment (n=374 and 283, respectively) samples. This study suggests that antimicrobial usage on this farm did not alter the resident population of enterococci.