Antimicrobial resistance of Enterococcus isolated from pre-chill swine carcasses

ABSTRACT

Background: As a result of the extensive use of antimicrobials in agriculture, animals have been implicated as possible reservoirs of resistant strains of bacteria. Enterococci are members of the normal flora of the gastrointestinaltract of human and animals. Because of their ubiquity, enterococci have been introduced in programs to evaluate thehazard of transmission of resistant bacterial strains through the food chain. The aim of this study was to assess theantimicrobial resistance profile of Enterococcus isolated from swine carcasses at the pre-chill step of processing.Material, Methods & Results: Pig carcasses were sampled at three commercial slaughterhouses (A, B and C). Oneach of two sampling occasions swabs of 100 cm2 areas were taken from each ham, back, belly and jowl of a total of14 pre-chill carcasses. Enterococci were isolated and counted in KF Streptococcus Agar, and typical colonies wereconfirmed by PCR assay targeting the tuf gene. Enterococcus isolates were tested for susceptibility to nine differentantimicrobial agents by agar disc diffusion. From a total of 252 carcasses sampled, 240 (95.2%) presented presumptivecolonies of Enterococcus in counts ranging from 0.02 log CFU.cm-2 to 2.9 log CFU.cm-2. All isolates were confirmedas belonging to the genus Enterococcus, and the great majority was identified as E. faecalis (218/240; 90.83%). Half(125/240; 52.1%) of the Enterococcus isolates were susceptible to all tested antimicrobials. No resistance to ampicillin, vancomycin or teicoplanin was found. The most frequent resistance was to tetracycline (42.5%), followed byerythromycin (26.7%), high level (HLR) streptomycin (20.4%), ciprofloxacin (13.8%), chloramphenicol (12.1%)and HLR-gentamicin (10.4%). Among the 115 resistant Enterococcus isolates, 55 (47.8%) were multi-resistant, andthe distribution of the most common profiles was related to the slaughterhouse...(AU)