In vitro Evaluation of Potential Probiotic Characteristics and Survival of Human and Foodborne Lactic Acid Bacteria (Lacticaseibacillus rhamnosus and Lactiplantibacillus plantarum) in Mice Gastrointestinal Tract

Probiotic properties of 6 human and foodborne Lactobacillus strains were investigated in vitro with comparison to standard strains (Lactiplantibacillus plantarum ATCC 8014 and Lacticaseibacillus rhamnosus ATCC53103). They included viability in acidic environment (pH 2.5), survival in presence of bile salt and pepsin-pancreatin, autoaggregation, surface hydrophobicity (an indirect parameter of colonization of intestine cells), co-aggregation with pathogens (Escherichia coli O157:H7, Salmonella enterica ATCC 13076 and Listeria monocytogenes ATCC 7644) and antibiotic resistance. In addition, different groups of mice were fed by lactic acid bacteria for 7 days and viability of strains in mice feces were analyzed. All bacterial strains showed high survival at pH 2.5 (>98%), simulated pancreatic juice (>90%), simulated gastric condition (>77%) and also high resistance against bile salt (>89%). L. rhamnosus M1, isolated from cow milk, showed the greatest average surface hydrophobicity (63.7%), auto-aggregation (80.6%) and co-aggregation. Different strains of L. plantarum had resistance to the tested antibiotics, except for M8, which was sensitive to kanamycin and chloramphenicol. Among L. rhamnosus strains, M1 and RHM were the most sensitive to antibiotics demonstrating susceptibility to erythromycin. Oral feeding of the isolated strains caused beneficial effect reducing microbial amount on Plate Count and MacConkey agars in mice feces during 7 days. L. rhamnosus M1 and L. plantarum M8 are considered to be the best suitable candidates for probiotic strains because they showed a wide range of antimicrobial properties, resistance to acid and bile and survival in gastric and intestinal colonization.