In vitro screening of lactic acid bacteria for multi-strain probiotics

The aim of this research was to screen and evaluate some probiotic properties of lactic acid bacteria strains isolated from 150 animal fecal samples, such as cows, pigs, chickens, and ducks. To achieve an objective, 81 isolates were tested for antimicrobial activity, tolerance to bile salts and acid, potential adhesion to cell surface, and in vitro adhesion. The results of the antimicrobial activity against pathogenic bacteria showed that, out of 81 isolates, 61, 59, 43, 78, and 79 isolates had antimicrobial activity against Escherichia coli, Staphylococcus aureus, Salmonella sp., Shigella sp., and Kiebsiella sp., respectively. Most lactic acid bacteria (LAB) isolates were tolerant to 1.0% bile salts and were able to survive at pH 3.5 for 3 h. Twelve isolates were then evaluated on their hydrophobic character. Five isolates with probiotic properties were subsequently selected. Sequence analysis of 16S rDNA demonstrated that 2 isolates belong to Lactobacillus reuteri (strains P8 and P30), 2 to Lactobacillus plantarum (strains P6 and P31), and another one to Lactobacillus paraplantarum (strain P25). To assess their viability in broiler chicken diets, 3 strains, L. plantarum (strain P6), L. paraplantarum (strain P25), and L. reuteri (strain P30), containing 108 cfu/g were inoculated into a commercial chicken diet in the form of single strain and multi-strain preparations. We found that in all of the treatments, the numbers of viable cells of LAB (cfu/g of diet) were decreased below 107 cfu/g after 3 d of incubation. Therefore, based on our study, the single- and multi-strains may have a potential use as novel probiotics in broiler chicken diets.