Occurrence and antibiotic resistance of enterococci in ready-to-eat food of animal origin

The aim of this work was to determine which Enterococcus species could be isolated from food of animal origin and the significance of these enterococcal isolates according to their antibiotic resistance profiles. Ninety-two Enterococcus strains were isolated from retail food of animal origin in Olsztyn, Poland. They were classified as Enterococcus faecalis (44 strains), Enterococcus faecium (32 strains) or Enterococcus spp. (16 strains) by phenotypic method and confirmed by polymerase chain reaction (PCR). Susceptibility of these enterococcal strains to 15 selected antibiotics (ampicillin, penicillin G, gentamicin, streptomycin, vancomycin, teicoplanin, norfloxacin, levofloxacin, ciprofloxacin, tetracycline, tigecycline, rifampicin, nitrofurantoin, linezolid, fosfomycin, chloramphenicol and quinupristin/dalfopristin) was determined using the disk diffusion method according to the recommendations of Clinical and Laboratory Standards Institute (CLSI 2010, formerly NCCLS). All the investigated strains were sensitive to levofloxacin, ciprofloxacin and vancomycin. Antimicrobial susceptibility tests showed resistance phenotypes to a range of antibiotics widely administrated in humans such as tetracycline, nitrofurantoin and quinupristin/dalfopristin.   Key words: Enterococcus spp., antibiotic resistance, food, animal origin, food safety