Screening of the Enterocin-Encoding Genes and Antimicrobial Activity in Enterococcus Species

Abstract

In the current study, a total of 135 enterococci strains from different sources were screened for the presence of the enterocin-encoding genes entA, entP, entB, entL50A, and entL50B. The enterocin genes were present at different frequencies, with entA occurring the most frequently, followed by entP and entB; entL50A and L50B were not detected. The occurrence of single enterocin genes was higher than the occurrence of multiple enterocin gene combinations. The 80 isolates that harbor at least one enterocin-encoding gene (denoted "Gene(+) strains") were screened for antimicrobial activity. A total of 82.5% of the Gene(+) strains inhibited at least one of the indicator strains, and the isolates harboring multiple enterocin-encoding genes inhibited a larger number of indicator strains than isolates harboring a single gene. The indicator strains that exhibited growth inhibition included Listeria innocua strain CLIP 12612 (ATCC BAA-680), Listeria monocytogenes strain CDC 4555, Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, S. aureus ATCC 29213, S. aureus ATCC 6538, Salmonella enteritidis ATCC 13076, Salmonella typhimurium strain UK-1 (ATCC 68169), and Escherichia coli BAC 49LT ETEC. Inhibition due to either bacteriophage lysis or cytolysin activity was excluded. The growth inhibition of antilisterial Gene+ strains was further tested under different culture conditions. Among the culture media formulations, the MRS agar medium supplemented with 2% (w/v) yeast extract was the best solidified medium for enterocin production. Our findings extend the current knowledge of enterocin-producing enterococci, which may have potential applications as biopreservatives in the food industry due to their capability of controlling food spoilage pathogens.

Influence of optimised commercial medium on bacteriocin production by <i>Enterococcus faecium

“…The supplementation with a nitrogen source did not increase the production of enterocins, diverging from the data obtained by some authors Kim, Hall, and Dunn (1997) and Iyapparaj et al (2013). Furthermore, both isolates of these study have 3 enterocin-producing genes, which are entA, entB, and entP (Ogaki et al, 2016). They can be expressed differently in each treatment performed.…”

“…The isolates Efm20 and Efm22 were previously reported, by our group, to be good enterocin producers (Ogaki et al, 2016), which inhibits several pathogenic food bacteria, including several species of Listeria (unpublished data).…”

“…Bacteriocinogenic E. faecium strain Efm20 and strain Efm22 isolated from soft cheese were grown at 37°C for 18 hours in MRS broth (Himedia) (Furlaneto-Maia, Rocha, Henrique, Giazzi, & Furlaneto, 2014;Ogaki, Rocha, Terra, Furlaneto, & Maia, 2016). L. innocua CLIP 12612 was used as indicator strain.…”

“…After incubation in all treatments, the cells were recovered by centrifugation at 8.000 g for 15 min. and the pH of the cell free supernatant (CFS) was adjusted to 6.5 and treated with catalase, to avoid the presence of H 2 O 2 (Ogaki et al, 2016).…”

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

“…Screening for enterocin activity was performed using the spot-on lawn assay (OGAKI, et al, 2016). One milliliter of chloroform was deposited on the covers of plates of E. durans MF5 strains, previously incubated on BHI agar (Himedia) at 37 °C for 24 h, and closed for 20 min; the plates were subsequently opened to allow the residual chloroform to evaporate.…”