Virulence factors and antibiotic resistance in enterococci isolated from food-stuffs

A collection of 250 enterococci isolated from various food-stuffs were used to investigate seven virulence determinants and the microbial susceptibility of eight antibiotics. Species-specific PCR revealed the presence of E. faecalis (127 isolates), E. faecium (77 isolates), E. casseliflavus (21 isolates), E. mundtii (19 isolates) and E. durans (six isolates). Multiplex PCR for virulence factors showed that from a total 250 isolates, 221 (88.4%) carried one or more virulence-encoding genes. β-Haemolytic activity was also evident in enterococcal species other than E. faecalis and E. faecium. Species other than E. faecalis and E. faecium isolated from food are also seen to harbour the potential for virulence. Antimicrobial susceptibility testing using the disk diffusion method showed that of the total 250 isolates, 114 (46%) were resistant to cephalothin and 94 (38%) to ofloxacin. Lower antibiotic resistance was seen with ampicillin, chloramphenicol, gentamicin and teicoplanin. None of the isolates was found to be resistant to vancomycin. The results of this study show that food can play an important role in the spread of enterococci with virulence potential through the food chain to the human population.