Probiotic characterisation of Enterococcus faecalis strain isolated from a household dahi sample of Wayanad district, Kerala

Household dahi sample with good organoleptic properties from Wayanad district of Kerala was screened for lactic acid bacteria. Gram positive cocci exhibiting potential to ferment lactose was further characterised biochemically and later identified by 16srRNA sequencing as Enterococcus faecalis. The isolate was evaluated for its physiological and probiotic properties like temperature tolerance, salt tolerance and proteolytic activity. Probiotic properties like acid tolerance, bile tolerance, adhesion potential and antimicrobial activity against clinical isolate of E. coli were evaluated. Virulence based on haemolysis in blood agar was also done. The isolate was able to survive both 4o C and 45o C as well as salt concentration of 2 to 8 per cent. This remarkably proteolytic isolate was able to survive at pH 2 and 3 for 3 h and could tolerate bile concentration of 0.3 per cent for 3 h and 0.6 per cent for 1 h. Cell surface hydrophobicity was found to be 19.6 per cent and auto aggregation 80.39 per cent. The isolate could inhibit the growth of pathogenic E.coli by producing a zone of clearance of 19mm. Antibiogram revealed resistance to Ceftriaxone, Cefotaxime, Cefazolin and Vancomycin. The isolate produced alpha haemolysis in blood agar. Study revealed that detail biochemical and molecular level characterization is required for assessing probiotic potential of lactic acid bacteria from naturally fermented products.

Keywords: Enterococcus faecalis, dahi, probiotics