Isolation and characterization of lactobacilli from human faeces and indigenous fermented foods for their potential application as probiotics

This study was conducted to select Lactobacillus strains from various sources on the basis of their probiotic attributes, such as acid and bile tolerance, binding to intestinal cells, and antimicrobial activity. Twelve isolates were obtained from human and food sources and were evaluated against standard probiotic Lactobacillus rhamnosus GG (LGG). Isolates were also studied for their antibiotic susceptibility. Isolate Lactobacillus fermentum GPI-6 showed the best survival profile at 0.3% and 1% bile salt, as compared with LGG. Isolates Lactobacillus plantarum GRI-2 and Lactobacillus salivarius GPI-4 showed no reduction in survival rate at pH 2.5. As expected, isolates showed strain-specific differences when comparing various attributes. Isolates GPI-4, GPI-7, and FA-5 showed better adhesion to HT-29, while isolate GPI-4 adhered better to Caco-2 cells than did LGG. However, when studying their ability to compete with Escherichia coli O26:H11, isolates GPI-6 and GPI-7 significantly inhibited E. coli adhesion to both HT-29 and Caco-2 cells compared with LGG. In conclusion, isolates GPI-4, GPI-7, and FA-5 showed excellent binding ability and antagonistic activity and better tolerance to acidic pH (pH 2.5) and to different bile salt concentrations in comparison with LGG, and hence, they could be considered as potential probiotic candidates.