Inhibition of Dermatophyte Fungi by Australian Jarrah Honey.

Superficial dermatophyte infections, commonly known as tineas, are the most prevalent fungal ailment and are increasing in incidence, leading to an interest in alternative treatments. Many floral honeys possess antimicrobial activity due to high sugar, low pH, and the production of hydrogen peroxide (HO) from the activity of the bee-derived enzyme glucose oxidase. Australian jarrah () honey produces particularly high levels of HO and has been found to be potently antifungal. This study characterized the activity of jarrah honey on fungal dermatophyte species. Jarrah honey inhibited dermatophytes with minimum inhibitory concentrations (MICs) of 1.5-3.5% (/), which increased to ≥25% (/) when catalase was added. Microscopic analysis found jarrah honey inhibited the germination of conidia and scanning electron microscopy of mature hyphae after honey treatment revealed bulging and collapsed regions. When treated hyphae were stained using REDOX fluorophores these did not detect any internal oxidative stress, suggesting jarrah honey acts largely on the hyphal surface. Although HO appears critical for the antifungal activity of jarrah honey and its action on fungal cells, these effects persisted when HO was eliminated and could not be replicated using synthetic honey spiked with HO, indicating jarrah honey contains agents that augment antifungal activity.