Potential of enterocin from <i>Enterococcus durans</i> MF5 in controlling <i>Listeria</i> species

This research paper presents the characterization of an enterocin-producing <i>Enterococcus durans</i> MF5 isolate and the determination of the in vitro antilisterial activity of enterocin produced by this isolate, named Ent-MF5. PCR-based screening for bacteriocin biosynthetic genes revealed that <i>E. durans</i> MF5 harbors multiple enterocin-encoding genes (<i>ent</i> A, B, P and X), classified as class II bacteriocins and enterocin-P of <i>Enterococcus faecium</i> (sharing up to 99% similarity at the genetic level). <i>E. durans</i> MF5 is sensitive to eight clinically important antibiotics and does not possess cytolysin activator -<i>cyl</i>A, gelatinase -<i>gel</i>E and hyaluronidase -<i>hy</i>lA virulence genes. The antilisterial activity of Ent-MF5 was abolished by trypsin, α-chymotrypsin, protease and proteinase-K. Ent-MF5 showed thermal and pH stability. In addition, the activity of Ent-MF5 was unaffected in the presence of various surfactants (1% SDS, Triton X-100, Tween 20, and Tween 80). Ent-MF5 exhibited antimicrobial activity against <i>Listeria monocytogenes</i>, <i>Listeria innocua</i>, <i>Listeria ivanovii</i> and <i>Listeria seeligeri</i> at concentrations as low as 0.13 μg/ml. Ent-MF5 had a bactericidal effect against <i>L. monocytogenes</i> with a significant reduction in surviving cells at concentrations equal to or greater than 0.13 μg/ml. A 75-100% reduction in <i>L. monocytogenes</i> growth and bactericidal effect determined by CFU counts was observed following treatment with Ent-MF5 at 4.47 μg/ml at time points starting at 2 and 4 h, respectively. Ent-MF5 action is associated with <i>Listeria</i> cell membrane damage, as observed by flow cytometry and fluorescence microscopy. Thus, the effective antilisterial activity and stability of Ent-MF5 presents promising perspectives for application as biopreservatives in the food industry.