High inhibition of Paenibacillus larvae and Listeria monocytogenes by Enterococcus isolated from different sources in Tunisia and identification of their bacteriocin genes

A total of 300 isolates of Enterococcus, from different sources including faeces of poultry, cow and sheep, raw milk, ricotta cheese and water, in Tunisia, were screened for their antibacterial activity. Amongst them, 59 bacteriocin-producing strains were detected and identified by molecular methods. Genes encoding for entA, entP, entB, entL50A/B, AS-48 and bac31 bacteriocins were targeted by PCR. The bacteriocin-producing strains were assigned to the species Enterococcus faecium, Enterococcusfaecalis, Enterococcushirae, Enterococcusmundtii and Enterococcusdurans, respectively, 34, 19, 3, 2 and 1 isolates. Antimicrobial activity was specifically observed against different spoilage and pathogenic micro-organisms, such as Listeria monocytogenes, Listeriainnocua, Listeriaivanovii, Escherichia coli, Ent.faecalis, Staphylococcus aureus, Salmonella enterica serovar Enteritidis and Paenibacillus larvae. The inhibitory activity was totally lost after proteinase K treatment, thereby revealing the proteinaceous nature of the antimicrobial compound. Only three bacteriocin genes, namely entP, entA and entL50A/B were detected in the isolates included in this study. Enterocins A and P were the most frequent genes and they were found in 55 (93 center dot 2%) and 39 isolates (66 center dot 1%), respectively, followed by enterocin L50A/B present in 27 isolates (45 center dot 7%). These newly identified bacteriocin-producing enterococci have the potential to be used in bio-preservation of food as well as biological control of foulbrood disease.