Antagonistic Activity of Lactobacilli Isolated from Buffalo Milk and Yogurt against Some Food Pathogens in Golestan province

Lactic acid bacteria which are found in large amounts in dairy products, have antagonistic activity against many pathogenic microorganisms. In this study, the inhibitory effect of Lactobacillus strains isolated from buffalo milk and yogurt in Bandar Gaz city was investigated. Raw milk and yogurt samples were cultivated on MRS medium, incubating anaerobically at 37°C for 48 h. The suspected colonies were identified on the basis of Gram’s staining and biochemical tests. The antibacterial activity of the cell-free supernatant extracted from Lactobacillus strains was determined using the agar well diffusion method against standard strains including Shigella flexneri ATCC 12022 ، Salmonella typhimurium ATCC 14028 ، Vibrio paraheamolyticus ATCC 17802 ، Escherichia coli ATCC 11303 and Staphylococcus aureus ATCC 29213. A total 10 Lactobacillus strains were identified as L. plantarum, L. casei, L. acidophilus. The cell-free supernatant of L. plantarum A1 had a relatively strong inhibitory effect against S. aureus and a moderate inhibitory effect against E. coli and S. flexneri, while no inhibitory effect on V. paraheamolyticus and S. typhimurium growth. L. casei B1 showed a moderate inhibitory effect against S. flexneri and S. aureus. The supernatant of L. acidophilus R1 vs. S. aureus showed a moderate inhibitory effect and had an inhibitory effect on V. paraheamolyticus. The results of this study showed that Lactobacilli isolates had good inhibitory activity against some food pathogens, therefore further studies on their use as biopreservatives to prevent the survival and proliferation of microorganisms in food products are recommended.