Exploring the Genetic Diversity of Candida albicans in Animal Hosts: A One Health Perspective.

INTRODUCTION: Candida albicans is an important priority fungal pathogen that commonly colonizes humans and a wide range of animal hosts, although its population structure in wildlife remains poorly explored. METHODS: In this study, 41 C. albicans isolates obtained from Italian wild animals (European hedgehogs, wolves, foxes, badgers, roe deer and porcupine) were identified by hwp1-specific PCR and subsequently genetically characterized using ABC typing, mating-type locus analysis and multilocus sequence typing (MLST). RESULTS: Several isolates were heterozygous at the hwp1 locus, and one rare 850 bp homozygous variant was detected in animals for the first time. ABC typing assigned 27 isolates to genotype B, 10 to genotype A and 4 to genotype C. All isolates were heterozygous (a/α) at the mating-type locus. MLST analysis identified 116 alleles, including 20 novel alleles, and 36 diploid sequence types, of which 28 were newly described. Twenty-two isolates clustered within 11 clonal complexes shared with human isolates, whereas 19 were singletons. Animal isolates were distributed across nine established MLST clades, with no clear association with host species. However, nearest-neighbour analysis revealed partial but significant genetic segregation between human and animal isolates, suggesting a degree of host-associated population structuring. CONCLUSIONS: Overall, these findings indicate that animal-associated C. albicans populations represent a substantial and largely unexplored reservoir of genetic diversity and contribute to a better understanding of the population structure and ecology of this opportunistic pathogen within a One Health framework.