Evaluation of the activity and molecular characterisation of bacteriocins produced by E. faecium and E. faecalis isolated from different hosts against public health-threating pathogens.

The aim of the study was to assess the activity and genetic background of bacteriocins of E. faecium and E. faecalis isolated from different hosts against methicillin-resistant Staphylococcus aureus (MRSA), E. faecium and E. faecalis with vancomycin (VRE) and high-level aminoglycoside (HLAR) resistance, Streptococcus agalactiae, and Listeria monocytogenes. The research was carried out using qualitative method and partially purified bacteriocins. The occurrence of 12 bacteriocin genes was examined and their sequences were analysed. Bacteriocins showing inhibitory activity against indicator strains were isolated from 95 % of E. faecium and 50 % of E. faecalis gave positive results in qualitative method. The highest inhibitory activity of bacteriocins isolated from E. faecium was obtained against E. faecium (100-25600AU/ml), E. faecalis VRE/HLAR (100-12800AU/ml), and L. monocytogenes (100-6400AU/ml), while bacteriocins isolated from E. faecalis were active against L. monocytogenes (100-25600AU/ml). The lowest activity of bacteriocins isolated from both Enterococcus species was determined against S. agalactiae (100AU/ml) and MRSA (100-800AU/ml). The presence of at least one bacteriocin gene was detected in 95 % of E. faecium and 52 % of E. faecalis. Four genes encoding bacteriocins was found (entB, enxAB, entA, entP), with the highest frequency of entA (97 %) in E. faecium and entB (53 %) in E. faecalis. The changes observed in the nucleotides among the entA, entB, and enxAB genes did not affect the activity of the bacteriocins. To sum up, E. faecium and E. faecalis may be a source of bacteriocins inhibiting the growth of drug-resistant bacteria, such as MRSA, HLAR, VRE, and L. monocytogenes.