Screening of Locally Isolated Lactic Acid Bacteria for Use as Probiotics in Poultry in Iran

Abstract

A total of 250 chicken intestinal specimens were screened for the presence of lactic acid bacteria (LAB) by routine cultural, morphological and biochemical reactions. Based on the results, 75 isolates were identified as LAB and were characterized for their probiotic potential. During preliminary investigations, the viability of the isolated LAB strains under different environmental and stress conditions was evaluated. Three of the strains which appeared resistant to acidic pH values and high bile salt concentrations were selected for further detailed studies. Based on the biochemical reactions these strains were identified as, Lactobacillus acidophilus RNL26, Lactobacillus fermentum RNL 44, and Lactobacillus salivarius RNL 49. All three strains demonstrated enhanced inhibitory activity against gram positive species including Clostridium perfringens, Staphylococcus aureus and Listeria monocytogene, while L. fermentum RNL 44 was also inhibitory towards gram negative bacteria; Salmonella enteritidis and S. typhimurium. The antibacterial effect exerted by L. acidophilus RNL26 and L. salivarius RNL 49 appeared to be due to bacteriocin or bacteriocin like substance, as the neutralized and catalase treated supernatant fluid of both the strains retained their antibacterial activity. All three strains were further characterized for their cholesterol removal, aggregation, co-aggregation, and cell surface hydrophobicity under in vitro conditions. According to our results L. fermentum RNL 44 appeared to be a superior probiotic candidate compared to the other two studied probiotic strains, Lactobacillus acidophilus RNL26 and Lactobacillus salivarius RNL 49.