Lactobacillus strains are a major part of the probiotics, microflora of the intestine as well as of fermented
dairy products, and are found in a variety of environments. The aim of this study was to find out the ability of
bile salts and acid tolerance as well as antibacterial properties of the three lactobacillus strains namely
Lactobacillus acidophilus ATCC 20552, Lactobacillus casei DSM 20011 and Lactobacillus plantarum ATCC
14917. The acid tolerance test was studied under pH 2.0 and 3.0 with 6.5 as a control. The cell count for the acid
tolerance test was obtained at an interval of 0, 1, 2 and 3 hours, and was pour plated on Man Rogosa, and Sharpe
(MRS) agar to be incubated at 37 °C for 24 hours. All cells were selected for bile tolerance test in MRS broth
containing bile concentrations of 0 % as control and 0.1, 0.3, 0.5 and 0.7 % as test and antibiotic susceptibility.
Results showed that the three strains of Lactobacilli have ability to tolerate acid and bile salts and resistance to
0.4 % of phenol and were susceptible for streptomycin (10 μg), ampicilline (10 μg), chloramphenicol (30 μg),
erytromycin (15 μg), amoxicillin/clavulanic acid (30 μg) and rifampicin (5 μg). All strains have antimicrobial
activity against seven indicator bacteria included Bacillus cereus DSM 351, Escherichia coli ATCC 25922,
Staphylococcus aureus ATCC 12600, Listeria monocytogenes, Salmonella typhimurium ATCC14028,
Klebseilla pneumonia ATCC 1705 and Pseudomonas aeruginosa ATCC 43495. |
