Department of Microbiology, State University of Londrina, Londrina, Paraná, C.P. 6001, 86051990, Brazil.
Department of Food Technology, Federal Technological University of Paraná, Campus of Londrina-Paraná, Londrina, 86036-370, Brazil.
World J Microbiol Biotechnol. 2019 Jun 20;35(7):96. doi: 10.1007/s11274-019-2675-0.
The biofilm-forming ability of Listeria spp. is a concern to the food industry and health sectors. The aim of this study was to verify the inhibitory activity of bacteriocins produced by enterococci (Enterococcus faecium 20, 22 and 24 and Enterococcus faecalis 27) on developing biofilm and preformed biofilm of Listeria species. Bacteriocins were partially purified from cell free supernatant (CFS). L. monocytogenes 2032, L. innocua 2050 and L. ivanovii 2056 were selected to analyse the inhibitory effect of bacteriocins on biofilm biomass (crystal violet staining) and biofilm viability (XTT-reduction). The biomass of the developing and preformed biofilms of Listeria species were reduced (p < 0.05) in the presence of all bacteriocins tested. Overall, the reduction in biofilm biomass of developing biofilms was up to 87.4% for bacteriocin produced by E. faecium 22 (CFS) against L. ivanovii and up to 87.1% for CFS against L. monocytogenes. These findings are in accordance with those observed in confocal microscopy analysis. Most of the CFS-containing bacteriocin (CFS, CFS, CFS) were effective at decreasing the viability of biofilm cells from all Listeria species. The highest reduction in viability was observed for L. monocytogenes preformed biofilm cells (up to 98.7%), evidenced by fluorescence microscopy of propidium iodide-labelled cells. Scanning electron microscopy showed that cells of biofilm-treated bacteriocins displayed degenerative changes that may be indicative of cellular leakages. This study suggests that bacteriocins produced by enterococci have prospective applications to prevent biofilm formation and/or to reduce cell viability of formed biofilms of distinct Listeria species.
李斯特菌形成生物膜的能力是食品工业和卫生部门关注的问题。本研究旨在验证肠球菌（屎肠球菌 20、22 和 24 以及粪肠球菌 27）产生的细菌素对李斯特菌生物膜形成和已形成生物膜的抑制活性。细菌素从无细胞上清液（CFS）中部分纯化。选择单核细胞增生李斯特菌 2032、无害李斯特菌 2050 和伊氏李斯特菌 2056 来分析细菌素对生物膜生物量（结晶紫染色）和生物膜活力（XTT 还原）的抑制作用。在测试的所有细菌素存在的情况下，李斯特菌生物膜的生物量（p<0.05）减少。总体而言，屎肠球菌 22 产生的细菌素（CFS）对伊氏李斯特菌的生物膜生物量减少高达 87.4%，对单核细胞增生李斯特菌的减少高达 87.1%。这些发现与共聚焦显微镜分析观察到的结果一致。大多数含有细菌素的 CFS（CFS、CFS、CFS）对所有李斯特菌生物膜细胞的活力均有效。用碘化丙啶标记细胞进行荧光显微镜观察时，发现对李斯特菌已形成生物膜细胞的活力降低最大（高达 98.7%）。扫描电子显微镜显示，用细菌素处理的生物膜细胞显示出退行性变化，这可能表明细胞渗漏。本研究表明，肠球菌产生的细菌素具有预防生物膜形成和/或降低不同李斯特菌生物膜形成细胞活力的潜在应用。
