Isolation and identification of Enterococcus faecium from seafoods: antimicrobial resistance and production of bacteriocin-like substances.

A collection of isolates from uncooked seafoods (molluscs, fish, and fish fillets) were identified as Enterococcus faecium species and studied in further detail. Isolates were clustered in well-defined genomic groups according to food origin after ERIC-PCR analysis. Four isolates (FR 1-2, FB 1-3-B, FB 3-1, FTA 1-2) decarboxylated lysine, ornithine, and tyrosine. Isolate FR 1-2 also decarboxylated histidine. Most isolates were sensitive to antibiotics of clinical use, but resistance was detected more frequently towards nitrofurantoin (50%), erythromycin (33.33%) or rifampicin (33.33%) to quinupristin/dalfopristin (12.5%). Resistance to beta-lactams or vancomycin was not detected. The enterococcal antigen A was the presumed virulence trait detected most frequently. None of isolates carried haemolysin/cytolysin genes. Twelve isolates produced anti-listerial activity. Among them, seven isolates also produced bacteriocin-like inhibitory substances against other enterococci, and one isolate was also able to inhibit Staphylococcus aureus. Three isolates only were active against Listeria monocytogenes, and two only were active against enterococci. One bacteriocinogenic isolate carried the enterocin A structural gene, but genes corresponding to other enterocins (EntB, EntP, EntQ, Ent1071, EntL50A/EntL50B, and Ent31) were not detected. Bacteriocin-producing enterococci lacking undesirable traits (such as antibiotic resistance or biogenic amine production) or their produced bacteriocins could be potential candidates to aid in preservation of seafoods and other food products as well.