Inhibition of Dermatophyte Fungi by Australian Jarrah Honey

Abstract

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 (H2O2) from the activity of the bee-derived enzyme glucose oxidase. Australian jarrah (Eucalyptus marginata) honey produces particularly high levels of H2O2 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% (w/v), which increased to ≥ 25% (w/v) when catalase was added. Microscopic analysis found jarrah honey inhibited the germination of Trichophyton rubrum conidia and scanning electron microscopy of mature T. rubrum 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 H2O2 appears critical for the antifungal activity of jarrah honey and its action on fungal cells, these effects persisted when H2O2 was eliminated and could not be replicated using synthetic honey spiked with H2O2, indicating jarrah honey contains agents that augment antifungal activity.

Bisphosphonates synergistically enhance the antifungal activity of azoles in dermatophytes and other pathogenic molds

“…Oxidative stress was measured in drug-treated T. rubrum using ROS-sensitive indicator DCFDA as described previously (34). Coverslips with drug-treated T. rubrum R-218 hyphae were prepared as described above.…”

Natural bioactive compounds of honey and their antimicrobial activity

“…Several in vitro and in vivo studies and researches have been conducted on the properties of honey: antibacterial, antifungal, antiviral and antiprotozoal (Mohammed et al 2017;Rani et al 2017;Semprini et al 2018;Guttentag et al 2021). The antimicrobial potential of honey varies considerably, it mostly depends on the botanical origin of the flowers, geographic source, season, harvest, storage conditions (Irish et al 2011;Anthimidou and Mossialos 2013), age and the health of bee colonies (Ibarguren et al 2010;Aween et al 2012a;Mathialagan et al 2018).…”

“…Mulu et al (2010) stated that Ethiopian honey treated the resistant strains of C. albicans in HIV-positive patients. Guttentag et al (2021) disclosed in their in vitro assays that Australian honey (Table 1) inhibits conidial germination and damages the structure of hyphae in Trichophyton rubrum. Some Egyptian single--flower honeys (Table 1) have shown some antifungal and antimycotic properties against Epidermophyton species, Trichosporon and Microsporum (El-Gendy 2010).…”

Towards a Better Understanding of Nutritional and Therapeutic Effects of Honey and Their Applications in Apitherapy

“…Furthermore, this variety of honey is considered to be a biofilm reducer for Candida species at concentrations that range between 50% and 75% (w/v). Further relevant academic work has suggested that the production of H 2 O 2 is critical for the antifungal activity of honey, but still not sufficient, as its level in honey's composition was too low to manifest a potent activity against some pathogenic fungi [180]. This can lead us to the conclusion that there are other compounds that act may as enhancing factors for the observed antifungal activity.…”