Antifungal Resistance and Synergistic Therapy in Candida Spp. Isolated From Bottlenose Dolphins Under Human Care: Implications for One Health Management.

INTRODUCTION: Routine antifungal susceptibility testing in animals is uncommon, yet increasingly relevant as antifungal resistance rises among marine mammals under human care. Despite the critical health risks posed by fungal infections, little research addresses multidrug-resistant Candida spp. in marine mammals under human care. This study aims to investigate the prevalence and antifungal susceptibility profiles of Candida species isolated from faecal and blowhole samples of bottlenose dolphins (Tursiops truncatus) under human care and to evaluate the in vitro efficacy of antifungal combination therapies within a One Health framework that considers environmental reservoirs and potential zoonotic risks. METHODS: Candida species were isolated from 14 faecal and 9 blowhole exhalate samples of 7 bottlenose dolphins. Minimum inhibitory concentrations (MICs) were determined through broth microdilution, revealing resistance to commonly used azoles (itraconazole, posaconazole, voriconazole and fluconazole). Synergy tests of antifungal combinations indicated that certain drug pairings could enhance treatment efficacy against resistant strains. Environmental monitoring of pool water samples identified Candida spp. using fluorescent in situ hybridization (FISH) a more sensitive diagnostic tool compared to traditional culture-based methods. RESULTS: In this study, Candida species (C. albicans, C. tropicalis, C. parapsilosis and N. glabratus) were isolated from faecal and blowhole exhalate samples of seven bottlenose dolphins (T. truncatus) to evaluate susceptibility profiles. To the best of our knowledge, this is the first study to report multidrug-resistant Candida spp. in dolphin faeces and blowholes and to assess the in vitro efficacy of synergistic antifungal treatments. CONCLUSION: This study underscores the importance of routine antifungal susceptibility testing and environmental surveillance in managed-care marine mammals to mitigate infection risks within a One Health framework. SUMMARY: Increases of antifungal resistance underscore the need for One Health approach. The in vitro synergy tests to identify appropriate treatment for candidiasis in bottlenose dolphins. FISH, complementary tool to detect Candida spp. in the water environment. Control the spread of drug-resistant Candida to enhance both animal and human health safety.