Discrimination between Pseudogymnoascus destructans, other Dermatophytes of Cave-dwelling Bats, and related innocuous Keratinophilic Fungi based on Electronic-nose/GC Signatures of VOC-Metabolites produced in Culture

摘要

White-nose syndrome (WNS), caused by the fungal dermatophyte (Pseudogymnoascus destructans), is considered the most important disease affecting hibernating bats in North America. The identification of dermatophytic fungi, isolated from the skins of cave-dwelling bat species, is necessary to distinguish pathogenic (disease-causing) microbes from those that are innocuous. This distinction is an essential step for disease diagnoses, early detection of the presence of microbial pathogens prior to symptom development, and for discrimination between microbes that are present on the skins of hibernating bats. Early detection of P. destructans infections of bats prior to symptom development is essential to provide effective early treatments of WNS-diseased bats which significantly improves their chances of survival and recovery. Current diagnostic methods using quantitative polymerase chain reaction (qPCR) for the detection of the microbes on bats require invasive methods (skin swabs) that tend to arouse hibernating bats resulting in consumption of valuable fat reserves that reduce their chances of winter survival. Also, qPCR only indicates the presence and quantity of fungal inoculum on bat skin, but does not indicate that the fungus has infected the host or that a state of disease exists since substrate fungal DNA used for PCR comes from outside of the host (on the surface of the skin) rather than from within the host (in deep subdermal layers of the skin). Consequently, we are developing non-invasive methods for the early detection of WNS-disease and other microbes of bats based on their production of unique mixtures of volatile organic metabolites that may be detected using a dual-technology, electronic-nose/gas chromatography device for identifying and discriminating between the microbial metabolites produced in pure cultures. We determined that the Heracles II e-nose system was effective in discriminating keratinophilic fungal species using principal component analysis (PCA) of smellprints signatures coupled with discrimination index (DI) and gas chromatographic retention times (RTs) of major VOC GC-peaks produced in culture headspace.