Effect of gamma radiation on the antibacterial and antibiofilm activity of honeydew honey

A variety of honeys have been clinically tested in wound care; some of these have obtained status “medical-grade honey”. Honey-containing licensed wound care products must undergo a sterilization process by gamma radiation. However, even though the antibacterial activity of honey seems not be affected by gamma radiation, no studies have been performed to assess its influence on particular honey antibacterial compounds. Therefore, the aim of this study was to investigate the effect of gamma radiation at the levels of 10, 20 and 30 kGy on glucose oxidase-mediated generation of hydrogen peroxide (H2O2) and bee defensin-1 in fir honeydew honey. We found that gamma radiation did not affect the overall antibacterial activity of honeydew honey; however, the concentration of defensin-1 was significantly reduced in irradiated honey. H2O2 levels were not elevated in irradiated honey when compared to non-irradiated honey. Furthermore, the antibiofilm activity of irradiated honey was not negatively affected as it effectively reduced established biofilms of Staphylococcus aureus and Pseudomonas aeruginosa. These results demonstrate that gamma radiation, at the doses mentioned above, does not result in significant alterations in the antibacterial and antibiofilm activity of honeydew honey. However, low molecular weight proteins and peptides such as defensin-1 may aggregate in irradiated honey.