The effects of Korean propolis against foodborne pathogens and spores of Bacillus cereus

초록

This study was performed to evaluate the effects of Korean propolis against foodborne pathogens and spores of Bacillus cereus. Propolis is a hard resinous substance made by bees and is known as one of natural antibiotics. The antimicrobial effects of the Korean propolis was tested against foodborne pathogens including Gram-positive (Bacillus cereus, Listeria monocytogenes, Staphylococcus) and Gram-negative (Salmonella typhimurium, Escherichia coli, Pseudomonas fluorescence) bacteria by agar diffusion assay. In general, Gram positive bacteria were more sensitive than were Gram negative bacteria. The vegetative cells of Bacillus cereus was the most sensitive among the pathogens tested. Propolis had a minimum inhibitory concentration (MIC) of 0.36 mg/ml against B. cereus on agar medium. In liquid broth, treatment with 0.18 mg/ml propolis showed bactericidal effect against B. cereus. Bacillus cereus vegetative cells exposed to 0.72 mg/ml of propolis lost their viability within 20 min. Against spores of B. cereus, propolis acted sporostatically under the same concentration and inhibited germination up to 30 hours compared to control. Higher concentration of propolis was required to inhibit spores of Bacillus cereus. The bactericidal and sporostatic action of propolis were dependent on the concentration of propolis used and treatment time. The antimicrobial effect of propolis in this study suggests potential use of propolis in food application to improve food safety.