Some probiotic characteristics of Lactobacillus species isolated from feces of infants fed with breast milk

In this study, 15 lactobacilli from the Gazi University, Faculty of Science Biotechnology Laboratory culture collection were used as material. The bacteria were formerly isolated from faces of breast-fed newborn babies and were identified based on the 16S rDNA region. The aims of the study were to determine their lactic acid, hydrogen peroxide and exopolysaccharide (EPS) production, antibiotic susceptibility, antimicrobial activity, resistance to acid and bile tolerance. The coagregasyon and autoaggregation capabilities, hydrophobicity, and cholesterol removal of the Lactobacillus casei LB74 and L. casei LB61 strains that exhibit a high EPS production were also determined. In order to determine the amount of acid produced by the strains, two different medium were used. Skim milk agar medium provided a higher acid production (1.05%-2.79%). The quantities of hydrogen peroxide production of the bacteria ranged between 0.68-3.83 mg / mL and the quantities of EPS produced rangend between 142.99-425.16 mg/L. Disk diffusion method has been used to determine the sensitivity of the strains to various antibiotics. The strains were 100% sensitive against penicillin G, chloramphenicol, and amoxicillin but 100% resistant against streptomycin and vancomycin. The antimicrobial effect of the lactobacilli strains over the pathogenic bacteria (Escherichia coli ATCC 11229, Staphylococcus aureus ATCC 25923, Listeria monocytogenes ATCC 7644, Salmonella enteritidis ATCC 13076, Salmonella typhimurium MU 80, Pseudomonas aeruginosa ATCC 27853) that cause disease in infants were %93.3, %66.6, %86.6 and %100, respectively. The bacteria viability decreased at decreasing and increasing bile acid concentrations and the data is statistically significant. Autoaggregation and coagregasyon (E. coli ATCC 11229, ATCC 7644 strains of Salmonella enteritidis and Listeria monocytogenes) abilities of the strains with high EPS production were determined. % Autoaggregation value was determined at L. casei LB74 (%28.91) and % coagregasyon value was determined at L. casei LB61 (%31.08) by using the test bacteria Salmonella enteritidis. Strains exhibites hydrophobicity with chloroform (67.05 to 45.33%) and toluene (7.88 to 43.83%). Cholesterol removal of the strains also increased with higher bile concentrations.