Potent Inhibition of Pseudogymnoascus destructans, the Causative Agent of White-Nose Syndrome in Bats, by Cold-Pressed, Terpeneless, Valencia Orange Oil

Abstract

The causative agent of White-nose Syndrome (WNS), Pseudogymnoascus destructans, has been shown to be fatal to several species of bats in North America. To date, no compounds or chemical control measures have been developed which eliminates the growth of the fungus in the environment or in affected animals. In the current study, we evaluated the activity of cold-pressed, terpeneless orange oil (CPT) against multiple isolates of P. destructans in vitro. For all assays, a modified Kirby-Bauer disk diffusion assay was used. Standardized spore suspensions were prepared, adjusted to a specific optical density, and used to plate fungal lawns. Plates were incubated at either 15°C or 4°C for up to 6 months and checked at regular intervals for growth. Once controls had grown, zones of inhibition were measured (mm) on test plates and compared to those obtained using current antifungal drugs. All P. destructans isolates were completely inhibited by 100% CPT (10 μL) at 1 month of incubation regardless of temperature (4°C and 15°C). Complete inhibition persisted up to 6 months following a single exposure at this concentration. Of the standard antifungals, only amphotericin B demonstrated any activity, resulting in zone diameters ranging from 58 mm to 74 mm. CPT, at the highest concentration tested (100%), had no significant effect against a variety of other environmental organisms including various filamentous fungi, bacteria and aerobic actinomycetes. Given that CPT is relatively non-toxic, the possibility exists that the all-natural, mixture could be used as an environmental pre-treatment to eradicate P. destructans from bat habitats. Additional studies are needed to assess any undesirable effects of CPT on bat behavior and health and overall impacts on other members of the interconnected ecosystem(s).

Antifungal activity of selected essential oils against Fusarium culmorum and F. graminearum and their secondary metabolites in wheat seeds

“…A number of scientific investigations have proved the antimicrobial activity of EOs derived from various herbs and plants, including their biological activity towards many fungal plant, animal and human pathogens (Lang and Buchbauer 2012; Boire et al 2016; Grata 2016; Kumar et al 2016; Gabriel et al 2018). The antifungal mechanism of action of EOs is not yet completely understood.…”

Tools to study pathogen-host interactions in bats

“…Recently, a novel Streptomyces species with anti-fungal activity was identified in bats (Hamm et al, 2017). WNS has caused the death of millions of little brown bats in North America (Alves et al, 2014;Knudsen et al, 2013;Zukal et al, 2014) and this new compound amongst others (Boire et al, 2016) might help to curb the spread of WNS. Potential toxic effects of this drug can be tested in uninfected bat cell lines before testing them in live bats or other relevant animal models.…”

Antifungal activity of various essential oils against Saccharomyces cerevisiae depends on disruption of cell membrane integrity

“…They are known to have antioxidant (Yang et al, 2010), antibacterial (Reichling et al, 2009), antifungal (Hammer at al., 2004), antiplasmid (Schelz et al, 2006), antiviral, antiparasitic and insecticidal properties (Unal et al, 2009). It is clear from different studies on EOs which are defi ed 'generally regarded as safe' (GRAS) by the US' Food and Drug Administration that they have potential uses in medicine and applications in the cosmetic, pharmaceutical and food industries and also in cleaning products (Souza et al, 2007;Van Vuuren et al, 2009;Lima de Sousa et al, 2013;Bialon et al, 2014;Rajkowska et al, 2014;Boire et al, 2016).…”