Molecular analysis of seven Lactobacillus strains isolated from human origin in West of Mazandaran.

Colorectal cancer is considered to be an important cause of morbidity and mortality worldwide. Anti-cancer properties of probiotic lactic acid bacteria are considerable for treatment of cancers such as colorectal cancer. The aim of this study was to investigate the molecular characterization of probiotic bacterial isolates from collected stool specimens in west of Mazandaran province, in order to confirm the probiotic effect of isolated strains, so to compare their effect on cancer cell lineages, in future studies. In this study, out of 60 stool samples collected from healthy children and adult people, 50 bacterial strains were isolated. Antibiotic susceptibility was performed by 15 antibiotics for 7 strains. Then, pH and bile salts tolerance were measured in the strains. Molecular analysis of these strains was carried out by PCR-sequencing and their results were used to draw a phylogenetic tree. Of the 50 isolates, 7 isolates were lactic acid bacteria and two strains were completely probiotic. These strains were resistance to low pH and 0.3% bile salt. Molecular analysis showed that two strains SE and SG were probiotics related to Lactobacillus fermentum (86% homology) and Lactobacillus rhamnosus (61% homology) family, respectively, which were known as new strains. The results suggested that there are 7 strains with good tolerance in the gastrointestinal tract that have probiotic properties and this is the basis of future studies to evaluate their anti-tumor properties and ultimately oral administration.