Antimicrobial effects of chitosans on Escherichia coli O157:H7, Staphyloccus aureus and Candida albicans

摘要

The antimicrobial activities of chitosan oligosaccharide(chitohexaose) and two types of chitusans(M.W. 10,000 and M.W. 100,000) were examined against Escherichia coli O157:H7(ATCC 43894), Staphylococcus aureus(ATCC 144458) and Candida albicans(KFRI 432). Chitosan with molecular weight of 10,000 showed the strongest antimicrobial activities to E. coli O157:H7 and S. aureus, whereas chitohexaose acted most strongly against C. albicans. The most effective concentration of chitosan was measured to be 0.1 mg/mL for E. coli O157:H7 and S. aureus, and that of chitohexaose to be 1 mg/mL for C. albicans. Antimicrobial activities of chitosans and chitohexaose were maintained for 60 min after their treatment. They were found to induce leakage of intracellular proteins and nucleic acids from treated microorganisms. The efflux determined by assaying the #beta#-galactosidase leaked from the lactose-induced E. coli O157:H7 cells was observed to reach the highest level within 60 min after treatment with the antimicrobial agents and chitosan with 10,000 molecular weight gave the highest #beta#-galactosidase activity. Therefore, it is supposed that the antimicrobial activity of chitosan with its unique polycationic nature might be caused by its binding to anionic component(s) of the cell envelope and thereby inhibiting the membrane metabolism and/or leaking intracellular materials.