The objective of the present study was to isolate, identify and characterize new LAB strains with high probiotic potentials from Iranian (Isfahan) indigenous chickens. From 90 isolated LABs, 11 isolates had high growth rate under different stress conditions, including acid (pH 2.5), bile (0.5% oxgall), salt (6 15%) and temperatures 15 and 45 C, and their aggregation time was less than 120 min. Based on the molecular identification using 16S rDNA sequencing and phylogenetic analysis, the isolates belonged to two Lactobacillus salivarius and L. reuteri species. The isolates showed different tolerance to 16 clinically and veterinary relevant antibiotics, and most of them were resistant to or semitolerant of 7 15 different studied antibiotics. The Es11, Es12, Es3 and Es13 strains with resistance to or semi-tolerance of 15, 14 and 13 different antibiotics, respectively, were the most tolerant strains. The selected isolates showed a wide range of antimicrobial activity against 7 different pathogenic strains. All the isolates exhibited antagonistic activity against E. coli, Enterococcus hirae, Salmonella enterica and Staphylococcus aureus. The isolates Es6 and Es11 with high antagonistic activity and resistance against 6 of the studied pathogens were the most powerful antagonistic isolates. The values and types of adhesion to the Caco-2 cell cultures were significantly different (0 40 bacteria/Caco-2 cell), and the maximum adhesion was observed for the isolates Es6 and Es13 with 35 and 40 bacteria adhesion/cell, respectively. Finally, based on all the experiments, 7 strains, including Es1, Es6, Es7, Es11, Es12 and Es13, were selected for the further in vivo assays and possible use in the poultry industry.

Lactobacillus strains commonly used as probiotics which possess some properties such as resistance to gastric acidity and bile salts, production of antimicrobial compounds, the ability to modulate immune responses, and adhesion to gut tissues. This study aimed to isolate, identify, production and characterization of the probiotic strains. Total of 10 digestive tracts of chickens fed without antibiotics for presence of Lactobacillus spp was evaluated. All isolates were grown with different conditions like effect of temperature, pH, pepsine, bile, sodium chloride tolerance, aggregation, adhesion and antibiotic resistance test tested and then antibacterial activity was determined.In this study, 34 lactic acid bacteria were investigated as putative probiotic candidates. Based on the molecular identification using 16S rDNA sequencing the isolates belonged to Lactobacillus species. The strains showed potent antibacterial activity. The results on acid tolerance showed that all the strains tested survived at pH 2.0 to 5.5. L. agilis strain M18, L. salivarius strain M10, L.vaginalis strains M8 and M19, and L. crispatus strains Or2 and M10 showed the lowest sensitivity to pepsine. All the studied Lactobacillus strains were able to grow at both 15 and 45°C . Five Lactobacillus strains adhered well to the Caco-2 cells. The result of antibiotic resistance test of 34 lactic acid bacteria showed that most of them were resistant or intermediate. Based on 34 Lactobacillus strains, L. vaginalis strain M8 and L. reuteri strain M6 were selected for the further in vivo assays and possible eventual use as prophylactic and therapeutic agent.