Molecular characterization of antimicrobial Lactobacillus isolates and evaluation of their probiotic characteristics in vitro for use in poultry

A total of 113 lactic acid bacteria (LAB) were isolated from crop, gizzard, intestine and ceca regions of broiler chicken. Thirteen Lactobacillus isolates were selected based on their ability to grow on acidic pH and inhibition of enteric bacterial pathogens. They were identified using 16S rRNA and recA gene sequencing and evaluated for probiotic properties in vitro. These isolates showed effective inhibition against enteric bacterial pathogens like Escherichia coli and fungal pathogens, such as Aspergillus niger, A. flavus, Penicillium expansum, P. roqueforti, Candida albicans and Eurotium species. Analysis of 16S rRNA and recA gene sequences revealed that isolates belonged to Lactobacillus plantarum. They exhibited tolerance to bile salts (0.4%), gastric and intestinal conditions with bile salt hydrolase activity, suggesting their ability to survive during gastrointestinal transit and exert their probiotic action on host organism. They showed cell surface hydrophobicity (39-58%), auto-aggregation (60-80%) and co-aggregation with enteric pathogens like E. coli (49-62%) and Listeria monocytogenes (26-38%). Thus, they could potentially be bactericidal to pathogens and prevent their colonization on intestinal epithelium. They are non-pathogenic (-hemolytic) and negative for mucin degradation. Among these isolates, L. plantarum VJI21 and VJC1 showed more adherence to HT-29 cells than the enteric pathogen E. coli and prevented pathogen adherence to intestinal cells. L. plantarum VJI21 and VJC1, having potent probiotic properties, are considered good candidates for further studies in vivo towards the development of probiotic feed supplement in the poultry industry.