[Evaluation of antimicrobial potential of lactic acid bacteria isolated from chicken gastrointestinal tract]

ABSTRACT

Isolation of lactic acid bacteria with the potential to inhibit the growth of pathogenic E. coli and Salmonella.Samples from different parts of digestive tract of healthy chickens were cultured in MRS broth and incubated at 37°C for 24-48 hours in anaerobic and aerobic conditions. Then, plates containing MRS agar and Rogosa agar were inoculated with cells grown in MRS broth previously. Plates were incubated at 37°C for 24-48 hours. Different colonies on MRS agar plates were studied for cultural and morphological characters. The gram positive, catalase negative, non-spore forming cocci and bacilli which were unable to produce haemolysis were selected for inhibition assay against E. coli serotypes [O78K80, O2K1, O1K1] and Salmonella serotypes [pullorum, enteritidis, typhimurium]. The antagonistic properties of isolated lactic acid bacteria were studied by using agar spot test.Out of 659 isolated lactic acid bacteria, 139 isolates [21.09%] were able to inhibit growth of indicator strains used in this study. From 139 isolated lactic acid bacteria, of those which demonstrated antagonistic activity against the pathogens, 31 isolates were identified as Lactobacillus spp., and the 108 reminder isolates were Enterococcous spp. The isolated lactic acid bacteria were more efficient in inhibition of Salmonella than E. coli. The antagonistic activity observed in this experiment can be attributed to organic acids and bacteriocin production by lactic acid bacteria. As the source of isolation of lactic acid bacteria in this study was poultry, and their potential inhibitory effects against mentioned pathogens and considerto other essential criteria, it is foreseen that it would be possible to use these isolates as a feed additive in poultry production in order to reduce the risk of infection