Comparative evaluation of the antimicrobial actions of Greek honeys produced in the island of Lemnos and that of manuka against clinically important bacteria

Honey is a natural food that also has a long history of use in traditional medicine due its many biological properties, such as antimicrobial, antioxidant, anti-tumor and anti-inflammatory. In this study, the antimicrobial actions of eight honeys produced in various locations of the Lemnos island (northwest Greece) and that of manuka (origin of New Zealand, UMF 30+, licensed in many countries as topical medical preparation) were comparatively evaluated against ten clinically relevant bacteria, including five Gram-positive (Staphylococcus aureus, S. epidermidis, Enterococcus faecalis, Listeria monocytogenes and Bacillus cereus) and five Gram-negative (Salmonella enterica serovars Enteritidis and Typhimurium, Escherichia coli O157:H7, Vibrio parahaemolyticus and Pseudomonas aeruginosa). To do this, the agar-well diffusion assay was applied to measure the diameter of inhibition zones (mm) of two selected concentrations for each honey (25 and 12.5 % v/v), while the minimum inhibitory and bactericidal concentrations (MICs and MBCs) of each sample were also calculated against two representative of the bacterial species (S. Typhimurium and S. aureus), following the broth microdilution and agar spot methods, respectively. The water activity, pH and pollen composition of each honey were also determined. Results revealed that all the Lemnos honeys presented antibacterial action which was for some samples even superior to that of manuka, highlighting their further promising exploitation as natural antimicrobial systems for use in foods and medicine.