Vancomycin resistance and antibiotic susceptibility of enterococci in raw meat

The purpose of this study was to investigate antimicrobial resistance, in particular to vancomycin, of enterococci in samples (100) of meat (beef, chicken, turkey, lamb, and pork) sold in retail outlets of Catanzaro (Italy). Enterococci were identified to the species level. Antimicrobial susceptibility tests for a large spectrum of antibiotics including glycopeptides were performed by the disk diffusion method. Kappa statistic was used to evaluate associations of resistance to vancomycin with other antimicrobials. Enterococci were isolated from 45% of the samples, mostly from chicken meat (65.4%). Overall, 29% of samples were contaminated by vancomycin-resistant enterococci (VRE), whereas among those positive they represented 64.4% of isolates. Higher prevalence of vancomycin resistance was found in chicken samples (76.5%). The overall resistance to teicoplanin (TRE) was 30%, whereas among those positive, TRE represented 66.7% of isolates. The most frequent isolates were Enterococcus faecium (35.6%) and Enterococcus faecalis (33.3%). Resistance to vancomycin and teicoplanin was observed in 75% and 78.5% of E. faecium, and in 40% and 46.7% of E. faecalis, respectively. Most strains were susceptible to ampicillin (80%), while 88.9% were resistant to methicillin. The most effective antimicrobials were imipenem (73.3% susceptible) and rifampin (80%). The highest prevalence of resistance was for streptomycin (88.9%), tetracycline (84.4%), and erythromycin (75.6%). Resistance to vancomycin was significantly associated to methicillin, teicoplanin, erythromycin, tetracycline, and chloramphenicol. Further investigations about enterococcal colonization and infections in community and hospital subjects are needed.