Resistance profile of Enterococcus spp. recovered from healthy poultry against antimicrobial growth promoters

REDONDO, LEANDRO M.; BUCCI, JESICA; DOMINGUEZ, JOHANA E.; REDONDO, ENZO A.; FERNÁNDEZ MIYAKAWA M.E.

atlanta

Congreso; International Poultry Scientific Forum: The Southern Poultry Science Society 39th Annual Meeting The Southern Conference on Avian Diseases 59th Annual Meeting; 2018

Antimicrobial agents have been extensively used in food animals for growth promotion, resulting in selective pressure for antimicrobial resistant bacteria which can spread to humans. For this reason, global concern about development of antimicrobial resistance and transference of resistance genes from animal to human is rising. To understand the antimicrobial resistance evolution in food-borne bacteria under commercial productive conditions, and as a technical service to poultry producers, we have been monitoring the susceptibility to antimicrobial agents using indicator bacteria isolated from intensive farming systems. Enterococci were selected as indicator microorganisms, because they are widely distributed in the environment, and they are opportunistic pathogens with the ability to acquire and transfer antimicrobial resistance. The aim of the present study was to investigate antimicrobial susceptibility profiles of Enterococcus spp. isolates collected from healthy broiler chickens in commercial farms.A total of 192 isolates of Enterococcus spp. were obtained from 53 broiler farms. The minimum inhibitory concentration (MICs) for antimicrobials commonly used in poultry commercial farms as growth promoters was calculated by broth microdilution method. To define MIC epidemiological cut-off, MIC from poultry isolates were compared with MIC values from E. fecalis ATCC 29212 and Enterococci strains from our bacteria collection. Poultry strains show high rates of resistance to avilamycin (93%), bacitracin (94%), flavomycin (99%), josamycin (81%) and lincomycin (86%). No clear reduction in susceptibility, but elevated MIC90 for enramycin and virginiamycin, were found in these chicken isolates in comparison to reference strains.In this study, we provide an estimation of antimicrobial resistance predominance in Enterococci isolates present in the environment of intensive production system. A wide range of resistance was identified against a number of commonly applied antimicrobial growth promoters in poultry farms. Works like this are the first step towards a better understanding of the impact of antimicrobial livestock use in the generation and spread of antimicrobial resistance