The effects of Korean propolis against foodborne pathogens and transmission electron microscopic examination

Abstract

This study was performed to evaluate the effects of Korean propolis against foodborne pathogens and spores of Bacillus cereus and to investigate the antimicrobial activity against B. cereus structure by transmission electron microscopy (TEM). The antimicrobial effects of the Korean propolis were tested against foodborne pathogens including Gram-positive (B. cereus, Listeria monocytogenes and Staphylococcus aureus) and Gram-negative (Salmonella typhimurium, Escherichia coli and Pseudomonas fluorescence) bacteria by agar diffusion assay. Gram-positive bacteria were more sensitive than were Gram-negative bacteria. The vegetative cells of B. cereus were the most sensitive among the pathogens tested with minimum inhibitory concentration (MIC) of 0.036 mg/μl of propolis on agar medium. Based on MIC, sensitivity of vegetative cells of B. cereus and its spores was tested in a nutrient broth with different concentrations of propolis at 37°C. In liquid broth, treatment with 1.8 mg/ml propolis showed bactericidal effect against B. cereus. B. cereus vegetative cells exposed to 7.2mg/ml of propolis lost their viability within 20 min. Against spores of B. cereus, propolis inhibited germination of spores up to 30 hours, compared to control at higher concentration than vegetative cells yet acted sporostatically. The bactericidal and sporostatic action of propolis were dependent on the concentration of propolis used and treatment time. Electron microscopic investigation of propolis-treated B. cereus revealed substantial structural damage at the cellular level and irreversible cell membrane rupture at a number of locations with the apparent leakage of intracellular contents. The antimicrobial effect of propolis in this study suggests potential use of propolis in foods.

Antimicrobial activity, phenolic profile and role in the inflammation of propolis

“…As it can be seen in Table 3, the propolis showed greater activity against Gram-positive bacteria than against Gram-negative. These results are in agreement with those of Vardar-Ünlü et al (2008) and Kim and Chung (2011). This may be explained by the structural differences of the bacterial cell wall of Gram-positive and Gram-negative bacteria.…”

Czech Ethanol‐Free Propolis Extract Displays Inhibitory Activity against a Broad Spectrum of Bacterial and Fungal Pathogens

“…Numerous authors addressed the effects of ethanolic propolis extracts of various geographic origins against L. monocytogenes , including isolates, ATCC and NCTC strains, reporting MIC 40 to 1600 μg/mL (Stepanović and others ; Kalogeropoulos and others ), and inhibition zones 10 to 13 mm (Stepanović and others ). Several other papers reported similar effects (Diğrak and others ; Kim and Chung ). Besides the ethanolic extracts, Diğrak and others () documented inhibitory effects of propolis lipid extract (19.8 μg per disc), and propolis fatty acids extract (600 μg per disc).…”

Antimicrobial and antioxidant activities of different propolis samples from north‐western Algeria

“…These results are in agreement with those of Vardar‐Ünlü et al . () and Kim & Chung (). This may be explained by the structural differences of the bacterial cell wall of Gram‐positive and Gram‐negative bacteria.…”