Antibacterial activity of honeys produced in Mount Olympus area against nosocomial and foodborne pathogens is mainly attributed to hydrogen peroxide and proteinaceous compounds

The antibacterial activity of nine honeys produced in Mt. Olympus area (Greece) against five major nosocomial and foodborne pathogens was assessed by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) determination. Furthermore, MICs of treated honeys with catalase or proteinase K were determined and compared with those of untreated honeys. The MIC values of honeys against Acinetobacter baumannii and Klebsiella pneumonia varied from 6.25% (v/v) to 12.5% (v/v) while manuka MIC value for all tested strains has been determined at 12.5% (v/v).Honeys that tested against Citrobacter freundii, Salmonella infantis, and Salmonella typhimurium have shown MICs ranged from 12.5% (v/v) to 25% (v/v). The MBC values of honeys, including manuka honey, against all bacterial strains were determined at the same concentration as of MIC values thus indicating significant bactericidal activity exerted by all honeys. Importantly, some honeys had exerted stronger antibacterial activity than manuka honey which is used to combat infections caused by multidrug resistant pathogens. Hydrogen peroxide and uncharacterized proteinaceous compounds were identified as the major antibacterial agents as it is reflected by elevated MIC values demonstrated by almost all catalase treated honeys (raised twofold up to fourfold) and several proteinase K treated honeys (twofold increase). Further research regarding the characterization of antibacterial agents present in Mt. Olympus honeys as well as elucidation of their molecular targets might lead to applications in medicine and food industry.