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

Abstract

Significance and Impact of the Study: Enterococci possess interesting properties not only for the food industry, but also for animal and human health. The antimicrobial potential of these bacteria includes principally bacteriocin-like molecules. With the aim of identifying bacteriocinogenic strains, a collection of 300 enterococci isolated from different origins were screened and their spectrum of action, as well as the gene encoding the bacteriocin, was determined. Fifty-nine bacteriocin-producing Enterococcus showed high activity against Listeria monocytogenes and Paenibacillus larvae, the causative agent of American foulbrood. Enterocins A, P and L50A/B were found in various combinations. The most important finding of this study is the growth inhibition of P. larvae due to bacteriocin-producing Enterococcus, which opens up the possibility to use these strains to control the disease in honeybees. AbstractA 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 bacteriocinproducing 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, Enterococcus faecalis, Enterococcus hirae, Enterococcus mundtii and Enterococcus durans, respectively, 34, 19, 3, 2 and 1 isolates. Antimicrobial activity was specifically observed against different spoilage and pathogenic micro-organisms, such as Listeria monocytogenes, Listeria innocua, Listeria ivanovii, 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 (93Á2%) and 39 isolates (66Á1%), respectively, followed by enterocin L50A/B present in 27 isolates (45Á7%). 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.

Antimicrobial activity of enterocin obtained from Enterococcus durans on Shiga-like toxin-producing Escherichia coli

“…While E. faecium and E. faecalis are known producers of enterocins, E. hirae, E. mundtii, and E. durans have been identified as potential producers (JAOUANI et al, 2014).…”

Current knowledge and perspectives of Paenibacillus: a review

“…Certain other bacterial species demonstrate antagonistic activity to P. larvae , including Bacillus polymachus which shows potential as a biocontrol agent [156]. Multiple Enterococcus species have demonstrated antagonistic activity to P. larvae , and this is believed to be due to the bacteriocin genes found in their genomes [157]. A novel P. larvae phage phiIBB-Pl23 produces an endolysin which effectively kills P. larvae while at the same time remains nontoxic to bees [158].…”

Safety and technological properties of bacteriocinogenic enterococci isolates from Tunisia

“…enterica serovar Enteritidis (Jaouani et al . ). Therefore, these enterococci strains have high potential to be used as protective bacteriocinogenic cultures in food preservation.…”

“…Among 59 enterococci previously reported to exhibit bacteriocinogenic activities against several pathogens (Jaouani et al . ), 55 strains (31 Enterococcus faecium , 18 Enterococcus faecalis , 3 Enterococcus hirae , 2 Enterococcus mundtii and one Enterococcus durans ) were used in this study. Cultures were maintained at −80°C in MRS broth (AES, Bruz, France) supplemented with 30% (v/v) glycerol.…”

“…aureus , Salmonella enterica serovar Enteritidis and Paenibacillus larvae (Jaouani et al . ). The strains were isolated from different sources, including animal faeces, water, ricotta cheese and bovine milk.…”