The Isolation of lactic acid bacteria from local dairy products of Gorgan township with the ability to inhibit the growth of some gastrointestinal pathogens

Isolation and identification of lactic acid bacteria from local products can play an important role in the introduction of unique types of probiotics. The present study was conducted in an attempt to isolate lactic acid bacteria from local dairy produced in the township of Gorgan which had the ability to inhibit the growth of some gastrointestinal pathogens. In order to isolate lactic acid bacteria, cheeses samples were sub-cultured on media cultures of MRS agar, M17 Agar , KAA and MRS+Vancomycin. Then, isolates were identified based on general morphological characteristics, biochemical and sugar fermentation tests. Using agar well diffusion, the antibacterial activity of culture supernatant of lactic acid bacteria was tested against four pathogenic bacteria. Among 24 samples of local cheeses and dooghs and 4 industrial samples, a total of 73 isolates were identified in which Lactobacillus casei was the most frequent isolate with with 34.24%. Lactobacillus casei and Lactobacillus acidophilus isolated from sheep's dough and sheep's cheese and Lactobacillus delbrucki and Lactobacillus ramenosus isolated from sheep's dough showed significant antibacterial activity against all pathogenic bacteria studied, namely, E. coli, S. aureus, B. cereus and C. freundii. Moreover, lactic acid bacteria isolated from industrial samples showed less antibacterial activity compared to isolates of local samples. Overall according to antagonistic effects of lactic acid bacteria isolated from of Gorgan’s local dairy products, it is recommended to evaluate their use as probiotic bacteria.