Culture-based characterization of the respiratory mycobiota and antifungal resistance in bottlenose dolphins under human care

Abstract

Fungal colonization and antifungal resistance in marine mammals remain critically understudied, despite growing recognition of their ecological and clinical importance. This study presents the first comprehensive culture-based assessment of the respiratory fungal community and antifungal susceptibility patterns in common bottlenose dolphins (Tursiops truncatus) maintained under human care. Using culture-based methods and differential incubation temperatures, we identified a diverse community of fungi from exhaled breath samples of ten dolphins, including clinically relevant yeasts and filamentous fungi. Aspergillus species were the most frequently isolated genus, with A. niger, A. terreus, and several previously unreported species in cetaceans such as A. glaucus and Fusarium dimerum. Among the yeasts, Candida albicans, Nakaseomyces glabratus, and Meyerozyma guilliermondii were recovered. Antifungal susceptibility testing revealed azole resistance in isolates of Candida and related species, Mucor, and Aspergillus spp., including multidrug-resistant profiles, while susceptibility to echinocandins and amphotericin B was preserved. Notably, resistant isolates were detected in dolphins with a history of antifungal exposure, raising concern about potential selective pressure in managed settings. No pathogenic fungi were recovered from aquarium water, suggesting endogenous or close-contact sources. These findings highlight the need for routine fungal surveillance in marine mammal facilities and contribute novel data on host-associated fungal communities in aquatic mammals. More broadly, they underscore the importance of a One Health approach to fungal ecology and resistance in marine environments.