Isolation and Identification of Lactobacillus salivarius from Buffalo Milk and Evaluation of Its Antimicrobial Activity

Lactobacillus salivarius is a well-known probiotic bacterium, which is commonly isolated from gastro-intestinal tract of human and animals. The objectives of the present study were isolation, molecular detection and antimicrobial characterization of L. salivarius from buffalo’s raw milk.
A total number of 20 buffalo milk samples were collected aseptically from traditional buffalo farms in Urmia city, Iran. Milk samples were cultured and incubated on MRS agar, then suspected colonies were primarily determined according to their appearance and biochemical characteristics. Bacteria species were confirmed by polymerase chain reaction accompanied by restriction fragment length polymorphism (PCR-RFLP) and nucleotide sequencing of 16s rRNA gene. Antimicrobial activity of L. salivarius against pathogenic bacteria including Listeria monocytogenesis, Escherichia coli, Salmonella typhimurium, and Staphylococcus aureus was examined using agar-spot and agar-disk diffusion methods. Cell surface hydrophobicity of L. salivarius was also investigated according to microbial adhesion to xylene and toluene hydrocarbons.
From 60 suspected colonies which were selected according to phenotypic characteristics, 23 colonies were confirmed as lactic acid bacteria based on the molecular identification. Only one isolate belonged to L. salivarius. The antimicrobial activity results showed a significant growth inhibitory effect of L. salivarius on pathogenic bacteria comparing to standard bacteria. L. salivarius had the most inhibitory effect on S. aureus while it had the least inhibitory against S. typhimurium. The hydrophobicity of L. salivarius to xylene and toluene were 55.3% and 55.6% respectively.
Based on the results, the frequency of the Lactobacillus genus s was very low in buffalo milk. In addition, isolated L. salivarius had strong antimicrobial activity against pathogenic bacteria.