Abstract
Exophiala spp. are pigmented fungi ubiquitous in the environment. These filamentous black yeasts are opportunistic pathogens in warm- and cold-blooded animals, causing superficial and systemic mycoses.1-3 Phaeohyphomycoses caused by Exophiala spp. are an emerging disease in fish.2-5 Two Valentini pufferfish (Canthigaster valentini) from the same exhibit presented similarly within six weeks of each other, both with a white, cutaneous pustular lesion on their dorsum. Cytologies revealed a thick matt of necrotic cells admixed with septate, branching, parallel-walled fungal hyphae. Fungal culture and molecular identification through DNA sequencing of the Internal Transcribed Spacer and Tubby Bipartite Transcription Factor genes confirmed the isolate as Exophiala aquamarina. Despite in vitro antifungal susceptibility,6 anecdotal clinical experience suggests these fungal infections are highly resistant. Initial treatment with fluconazole prolonged immersion was unsuccessful. Topical therapy using Mohs’ Paste,7-9 a zinc chloride-based chemical fixation treatment from the 1930s and 1940s, was successful. Once applied, the superficial tissues are infiltrated and preserved, ultimately sloughing two weeks later. To hasten tissue healing of the exposed muscle and dermis, a POLYOX mucosal bioadhesive powder compounded with 0.0024% misoprostol, 2% phenytoin, and 2% enrofloxacin was applied topically every three days. Complete healing with epithelialization and pigmentation was achieved in 74 and 80 days with no evidence of recurrence. These cases provide evidence for a successful treatment option of a highly resistant fungal pathogen.
Acknowledgements
The author thanks the Adventure Aquarium Fish and Invertebrate husbandry team for their dedicated care of these fish and their assistance with treatments. The author also thanks the University of Connecticut’s Veterinary Medical Diagnostic Laboratory and University of Texas San Antonio’s Fungal Testing Laboratory for fungal culture and molecular identification.
* Presenting author
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