Safety Evaluation of Enterocin Producer Enterococcus sp. Strains Isolated from Traditional Turkish Cheeses

The purpose of this study was to determine the antimicrobial activity and the occurrence of bacteriocin structural genes in Enterococcus spp. isolated from different cheeses and also investigate of their some virulence factors. Enterococcus strains were isolated from 33 different cheeses. Enterococcus faecium (6 strains) and Enterococcus faecalis (5 strains) enterocin-producing strains were identified by 16S rDNA analyses. entA, entB, entP and entX structural genes were detected in some isolates. Multiple enterocin structural genes were found in 7 strains. None of the tested enterococci demonstrated β-haemolytic activity and only one strain has gelatinase activity. Six strains showed multiple antibiotic resistance patterns and in addition, vanA and several virulence genes were detected in many strains. Only E. faecalis MBE1-9 showed tyrosine decarboxylase activity and tdc gene was only detected in this strain.

Antibacterial activities of lactic acid bacteria isolated from cow faeces against potential enteric pathogens

BACKGROUND

The addition of sub therapeutic doses of antibiotics to cattle feed for growth promotion is a contributory factor to antibiotic resistance, thus an alternative to antibiotics is needed in animal feed additives.

OBJECTIVE

To determine the antimicrobial activity of cow's intestinal Lactic acid bacteria (LAB) against enteric commensals.

METHOD

Escherichia coli, Klebsiella species (spp) and LAB were isolated from thirty different cow faecal samples and the LAB identified by partial sequencing of 16S rRNA. The antimicrobial activity of the LAB was determined against the test Escherichia coli and Klebsiella spp.

RESULTS

Five species of LAB were isolated from thirty cow faecal samples and identified as Enterococcus hirae (8), Enterococcus durans (6), Enterococcus faecium (1), Enterococcus faecalis (1) and Weissella confusa (1). Viable cells and cell free supernatant (CFS) of the LAB were able to inhibit the growth of the test organisms with the largest zone of inhibition by the viable cells being 26mm against Escherichia coli CB6 produced by Enterococcus hirae CO6A while Weissella confusa CO29M and Enterococcus hirae CO2A produced the largest zones of inhibition (26mm) against Klebsiella CB2.

CONCLUSION

This study shows that LAB from cow faeces possess considerable antimicrobial activity against resistant Escherichia coli from the same environment.

Prevalence of bacteriocin activities and bacteriocin-encoding genes in enterococcal clinical isolates in Iran

The aim of the project was to isolate and characterize bacteriocin-producing enterococci, as well as determine the prevalence of enterocin structural genes in 187 enterococcal clinical isolates from the northwest of Iran. The isolates were screened for antibacterial activity against 15 different indicator strains. The proteinaceous nature of the antimicrobial substances was confirmed by sensitivity to proteinase K; their stability to heat treatment was tested at 60 °C and 100 °C for 20 and 10 min, respectively. The PCR method was applied to detect previously identified enterocin genes. Our results showed that 38 (20.3%) of the enterococcal isolates were considered to be potential bacteriocinogenic strains. Furthermore, genes encoding diverse bacteriocin are highly distributed among clinical enterococci, and the strains with multi-bacteriocin genes displayed high antimicrobial activity. Enterocin A, enterolysin A, and enterocin L50A/B were the most abundant structural genes detected in bacteriocinogenic strains. This work is the first survey on the prevalence of bacteriocin genes among clinical enterococci in Iran that has isolated a strain with high antimicrobial activity and sensitivity to clinically relevant antibiotics.

Partial purification and characterization of the mode of action of enterocin S37: a bacteriocin produced by Enterococcus faecalis S37 isolated from poultry feces

The aim of this research was to purify and characterize the mode of action of enterocin S37, a bacteriocin produced by Enterococcus faecalis S37, a strain recently isolated from the chicken feces. Enterocin S37 has a molecular weight comprised between 4 and 5 kDa. It remained active after 1 h at 80(o)C and at pH values ranging from 4.0 to 9.0. Furthermore, cell-free supernatant of Enterococcus faecalis S37 and purified enterocin S37 were active against Gram-positive bacteria including Listeria monocytogenes EGDe, L. innocua F, Enterococcus faecalis JH2-2, and Lactobacillus brevis F145. The purification of enterocin S37 was performed by ammonium sulfate precipitation followed up by hydrophobic-interaction chromatography procedures. Treatment of enterocin S37 with proteinase K, alpha-chymotrypsin, and papain confirmed its proteinaceous nature, while its treatment with lysozyme and lipase resulted in no alteration of activity. Enterocin S37 is hydrophobic, anti-Listeria and likely acting by depletion of intracellular K(+) ions upon action on K(ATP) channels. This study contributed to gain more insights into the mode of action of enterocins.

Assessment of environmental enterococci: bacterial antagonism, pathogenic capacity and antibiotic resistance

The properties of 166 environmental strains belonging to the seven enterococcal species were studied. Enterococci originated mainly from surface- and waste-waters. They were screened for the presence of enterocins, virulence factors, and antibiotic resistance. The presence of different enterocin genes (entA, entB, entP, ent31, entL50AB) was frequently observed in our enterococcal isolates, 109 strains contained at least one enterocin gene. The distribution of enterocin genes varied according to the species, the genes were present mainly in E. hirae and E. faecium. By enterocin spot assay, 10 isolates inhibited the growth of Listeria strains. To evaluate the pathogenic ability of isolates, the distribution of selected virulence genes (cylA, gelE and esp) was investigated, eleven strains were positive in some of these genes, five of them belonged to E. faecalis. Regarding the antibiotic resistance of isolates, only two strains were multiresistant and two strains (E. hirae and E. casseliflavus) were resistant to vancomycin.