-Enterococci isolated from a total number of 68 dairy products and 28 human fecal samples were screened for bacteriocin production. The incidence of the bacteriocin-production trait was highest among the cream samples (33.51%), followed by dahi samples (15.55%), raw milk samples (9.51%), Cheddar cheese (9.2%) samples and human feces (4.72%). The isolates showed antilisterial effect besides activity against other lactic acid bacteria. Sixty potent bacteriocin-producing isolates of enterococci were evaluated for the incidence of virulence characters for their safe exploitation. None of the isolates was found to exhibit gelatinase, DNAse or β-hemolysis activity. Furthermore, only 4 bacteriocin-producing isolates among 60 were observed to be vancomycinresistant. It was concluded that bacteriocin-producing Enterococcus strains lacking hemolytic activity and not carrying vancomycin resistance genes may be safely exploited as starter cultures, co-cultures or probiotics. Résumé -Incidence de la virulence d'isolats d'entérocoques produisant une bactériocine.Des entérocoques isolés de 68 produits laitiers et 28 échantillons fécaux humains ont été criblés pour leur production de bactériocine. L'incidence de ce caractère était maximale dans les échantillons de crème (33,51 %), suivis des échantillons de dahi (15,55 %), de lait cru (9,51 %), fèces humains (4,72 %) et fromage Cheddar (9,2 %). Outre leur activité contre les autres bactéries lactiques, les isolats avaient un effet anti-listeria. Soixante isolats d'entérocoques ayant la capacité de production de bactériocine ont été évalués pour l'incidence de leurs caractères de virulence sur leur sécurité d'emploi. Aucun des isolats n'a montré d'activité gélatinase, DNAse et β-hémolyse.

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In the present study 14 bacteriocinogenic strains of Enterococcus faecium isolated from dairy foods and faecal sample were evaluated for the presence of virulence determinants, production of biogenic amines and their susceptibility to various antibiotics. Genetic diversity among them was evaluated by RAPD-PCR method. Further, they were evaluated for their probiotic potential under in vitro trials. The efaAfm was the only virulence trait detected in all E. faecium and tyramine was the only biogenic amine produced by 9 tested strains. No strain was resistant to all antibiotics and for some strains, multiple resistances were observed. E. faecium FH 99 showed highest good ability to tolerate acid and bile, while good bile salt hydrolase activity and were able to assimilate cholesterol from growth media. These results suggest that the tested E. faecium are generally free from virulence traits and having good probiotic potential and may be exploit in dairy industry and probiotic preparations.

Enterococcus faecium FH 99 was isolated from human faeces and selected because of its broad spectrum of inhibitory activity against several Gram-positive foodborne spoilage and pathogenic bacteria. Ent. faecium FH 99 accumulates enterocin in large number in early stationary phase of the growth. The enterocin FH 99 was stable over a wide pH range (2-10) and recovered activity even after treatment at high temperatures (10 min at 100°C). The enterocin was subjected to different purifi cation techniques viz., gel fi lteration, cation exchange chromatography and reverse-phase high-performance liquid chromatography. The activity was eluted as one individual active fraction. SDS-PAGE revealed a molecular weight of less than 6.5 kDa. Studies carried out to identify the genetic determinants for bacteriocin production showed that this trait may be plasmid encoded as loss in both of the plasmids (size>chromosomal DNA) led to loss in bacteriocin production by Ent. faecium FH 99. Ent. faecium strain FH 99 is a newly discovered high bacteriocin producer with Activity Units 1.8 × 10 5 AU ml -1 and its characteristics indicate that it may have strong potential for application as a protective agent against pathogens and spoilage bacteria in foods.

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