Human Lactobacilli as antidiarrheal bio-agents : in vitro studies

Sanae Kaewnopparat, D. of Pharmaceutical Tech., F. of Pharmaceutical Sci., PSU.
Malyn Chulasiri, F. of Pharmacy, Mahidol U., Bangkok
Patricia L. Conway, The U. of New South Wales, Sydney, Australia
Corresponding e-mail : ksanae@ratree.psu.ac.th

Grant : University Development Commissions (UDC), Ministry of University Affairs
Presented : The 4th NRCT-JSPS Joint Seminar in Pharmaceutical Sciences, "Drug Development through Biopharmaceutical Sciences, November 24-26, 1998, Hat Yai, Songkhla
Key words : Lactobacillus spp., antidiarrheal ability, S. typhimurium, adhesion ability

Sixty Lactobacillus spp. were isolated form saliva and feces of healthy donor. They were stu-died for their antimicrobial effect and ability to grow and survive in different concentrations of bile and low pH. The primary results revealed 3 isolates, namely HL32, HL49, and HL64 possessed the promising antimicrobial ability against reference tested strains i.e., Staphylococcus aureus ATCC 25923, Escherichia coli ATCC25922, Pseudomonas aeruginosa ATCC27853, Bacillus cereus ATCC11778 and Candida albicans ATCC17023. They were also healthy to grow in high bile concentration and survive in low pH. These isolates were selected and studied for the effect on diarrhoeagenic bacteria, i.e. Aeromonas hydrophila, Escherichia coli, Vibrio cholerae, V. parahaem-molyticus, Shigella flexneri, Sh. sonii, Salmonlla typhimurium, Staphylococcus aureus, Bacillus cereus. The results showed the cultured brain heart infusion broth from these strains showed high inhibition ability to these clinical isolates. The further study, only HL32 was used as a model to examine its inhibition factors by using S. typhimurium as a representative of diarrhoeagenic bacteria. The overall results revealed that HL32 showed inhibition to the growth of S. typhimurium when they were grown together. The inhibition substances from HL32 were active at pH 4 and the activity gradually lost when the pH increased. The inhibition activity of these substances was stable after autoclaving at 121oC, 15 min but reduced when treated with catalase, trypsin, and protease. They were detected partly to be lactic acid, volatile short chain fatty acids, hydrogen peroxide and pro-tienaceus agent(s). The last substance(s) was shown to kill S. typhimurium and tend to change the morphology of bacterial cells under an electron microscope obserbation. HL32, HL49 and HL64 were also tested for their adhesion onto human enterocyte-like Caco-2 cells, results showed that HL49, HL64 had greater adhesion ability than HL32.
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