Where microbes colonizing skin surface may help maintain organism homeostasis, those that invade living skin layers cause disease. In bats, white-nose syndrome is a fungal skin infection that affects animals during hibernation and may lead to mortality in severe cases. Here, we inferred the amount of fungus that had invaded skin tissue of diseased animals. We used simulations to estimate the unobserved disease severity in a non-lethal wing punch biopsy and to relate the simulated pathology to the measured fungal load in paired biopsies. We found that a single white-nose syndrome skin lesion packed with spores and hyphae of the causative agent, Pseudogymnoascus destructans, contains 48.93 pg of the pathogen DNA, which amounts to about 1560 P destructans genomes in one skin lesion. Relating the information to the known UV fluorescence in Nearctic and Palearctic bats shows that Nearctic bats carry about 1.7 µg of fungal DNA per cm2, whereas Palearctic bats have 0.04 µg cm-2 of P. destructans DNA. With the information on the fungal load that had invaded the host skin, the researchers can now calculate disease severity as a function of invasive fungal growth using non-destructive UV light transillumination of each bat's wing membranes. Our results will enable and promote thorough disease severity assessment in protected bat species without the need for extensive animal and laboratory labor sacrifices.

• MeSH
• Ascomycota * metabolismus   patogenita   MeSH
• Chiroptera mikrobiologie   MeSH
• dermatomykózy * mikrobiologie   prevence a kontrola   terapie   veterinární   MeSH
• hibernace * MeSH
• křídla zvířecí mikrobiologie   MeSH
• kůže mikrobiologie   MeSH
• ultrafialové záření * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

While white-nose syndrome (WNS) has decimated hibernating bat populations in the Nearctic, species from the Palearctic appear to cope better with the fungal skin infection causing WNS. This has encouraged multiple hypotheses on the mechanisms leading to differential survival of species exposed to the same pathogen. To facilitate intercontinental comparisons, we proposed a novel pathogenesis-based grading scheme consistent with WNS diagnosis histopathology criteria. UV light-guided collection was used to obtain single biopsies from Nearctic and Palearctic bat wing membranes non-lethally. The proposed scheme scores eleven grades associated with WNS on histopathology. Given weights reflective of grade severity, the sum of findings from an individual results in weighted cumulative WNS pathology score. The probability of finding fungal skin colonisation and single, multiple or confluent cupping erosions increased with increase in Pseudogymnoascus destructans load. Increasing fungal load mimicked progression of skin infection from epidermal surface colonisation to deep dermal invasion. Similarly, the number of UV-fluorescent lesions increased with increasing weighted cumulative WNS pathology score, demonstrating congruence between WNS-associated tissue damage and extent of UV fluorescence. In a case report, we demonstrated that UV-fluorescence disappears within two weeks of euthermy. Change in fluorescence was coupled with a reduction in weighted cumulative WNS pathology score, whereby both methods lost diagnostic utility. While weighted cumulative WNS pathology scores were greater in the Nearctic than Palearctic, values for Nearctic bats were within the range of those for Palearctic species. Accumulation of wing damage probably influences mortality in affected bats, as demonstrated by a fatal case of Myotis daubentonii with natural WNS infection and healing in Myotis myotis. The proposed semi-quantitative pathology score provided good agreement between experienced raters, showing it to be a powerful and widely applicable tool for defining WNS severity.

• MeSH
• Ascomycota genetika   fyziologie   MeSH
• Chiroptera metabolismus   mikrobiologie   MeSH
• DNA fungální genetika   MeSH
• fylogeneze MeSH
• kožní nemoci mikrobiologie   patologie   MeSH
• křídla zvířecí mikrobiologie   patologie   účinky záření   MeSH
• lineární modely MeSH
• optické zobrazování MeSH
• stupeň závažnosti nemoci MeSH
• ultrafialové záření MeSH
• zvířata MeSH
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• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Pathogenic and non-pathogenic related microorganisms differ in secondary metabolite production. Here we show that riboflavin overproduction by a fungal pathogen and its hyperaccumulation in affected host tissue exacerbates a skin infection to necrosis. In white-nose syndrome (WNS) skin lesions caused by Pseudogymnoascus destructans, maximum riboflavin concentrations reached up to 815 μg ml(-1), indicating bioaccumulation and lack of excretion. We found that high riboflavin concentrations are cytotoxic under conditions specific for hibernation, affect bats' primary fibroblasts and induce cell detachment, loss of mitochondrial membrane potential, polymerization of cortical actin, and cell necrosis. Our results explain molecular pathology of WNS, where a skin infection becomes fatal. Hyperaccumulation of vitamin B2 coupled with reduced metabolism and low tissue oxygen saturation during hibernation prevents removal of excess riboflavin in infected bats. Upon reperfusion, oxygen reacts with riboflavin resulting in dramatic pathology after arousal. While multiple molecules enable invasive infection, riboflavin-associated extensive necrosis likely contributes to pathophysiology and altered arousal pattern in infected bats. Bioaccumulation of a vitamin under natural infection represents a novel condition in a complex host-pathogen interplay.

• MeSH
• Ascomycota klasifikace   genetika   patogenita   MeSH
• buněčná adheze MeSH
• Chiroptera mikrobiologie   MeSH
• dermatomykózy mikrobiologie   MeSH
• elektronová mikroskopie MeSH
• faktory virulence metabolismus   MeSH
• fibroblasty cytologie   metabolismus   mikrobiologie   MeSH
• fylogeneze MeSH
• interakce hostitele a patogenu MeSH
• křídla zvířecí cytologie   mikrobiologie   ultrastruktura   MeSH
• kultivované buňky MeSH
• membránový potenciál mitochondrií MeSH
• riboflavin metabolismus   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH