Antimicrobial Activity of Cell Free Supernatant of Indigeneous Lactic Acid Bacteria Against

Abstract

C.sakazakii is an opportunistic pathogen usually found in powdered infant formula (PIF) and causes severe infant diseases like meningitis and bacteremia. As the pathogen is usually encountered in infant formulae therefore, potential of lactic acid bacteria which is common inhabitant of human gut and used a starter in different fermented food preparation was evaluated for its inhibition. A total of nine different strains of Lactobacillus sp., isolated from different fermented food products of Himachal Pradesh were evaluated against different strains of C.sakazakii (ATCC 12868, E604, and lab strains i.e. N112, N15, N13) . The filter sterilized cell free supernatant (CFS) of the lactic cultures grown in MRS broth was used for determination of minimum inhibitory concentration against different strains of C.sakazakii. The MIC was determined using microtiter plate assay with 150 μl Tryptone Soy Broth and 10μl overnight grown C.sakazakii, followed by addition of 0-50μl of CFS of different lactic cultures. The other Lactobacillus sp. strains resulted in reduction of C.sakazakii by 79-86% at 50μl. Further, the antimicrobial activity was assessed by agar well assay where the strains 94,98 and 90 showed significant zone of inhibition ranging between 15-20mm. Further studies are in progress to elucidate the active moiety in the CFS for its antimicrobial activities. To further look at the potential component for antimicrobial activity ammonium sulphate precipitation was performed,and it was seen that a clear zone of inhibition was observed for 0-40% saturation against E604. Thereby, confirming that bacteriocins exhibited the antimicrobial activity. The presence of protein was confirmed by SDS PAGE which showed clear results of presence of protein at 0-40% saturation.