Antibacterial activity of lactobacilli from buffalo milk and yoghurt in Bandar-e Gaz, North-West Iran

A cross-sectional study was conducted from April to June 2016 to determine the inhibitory effect of Lactobacillus strains isolated from buffalo milk and yogurt in Bandar-e Gaz, Golestan province, North-West Iran. The raw milk and yogurt samples were collected and cultivated on MRS medium by anaerobical incubation at 37 °C for 48 h. The suspected colonies were identified on the basis of Gram’s staining and conventional 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 Escherichia coli ATCC 11303, Staphylococcus aureus ATCC 29213, Bacillus cereus ATCC 19115, Listeria monocytogenes ATCC 19111, E. coli and S. aureus isolates from local cheese samples. A total of 10 Lactobacillus spp. were isolated and identified as L. plantarum, L. casei, L. acidophilus. L. plantarum A1 and L. acidophilus R1 exhibited relatively strong inhibitory effect against S. aureus and B. cereus, respectively. Both isolates had no inhibitory effect against L. monocytogenes. L. casei B1 showed moderate inhibitory effects against L. monocytogenes. This study showed that Lactobacilli from buffalo dairy products had good inhibitory activity towards Gram-positive indicator organisms and were one of the best choices to control these pathogens in food products.