172 | Genetic diversity of Candida albicans in animal hosts

Lucilla Lo Re¹, Letterio Giuffrè¹, Silvia Crotti², Deborah Cruciani², Alice Ranucci², Orazio Romeo¹ | ¹Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Italy; ²Experimental Zooprophylactic Institute of Umbria and Marche “Togo Rosati”, Perugia, Italy.

Invasive fungal infections represent an escalating global health threat, with an estimated 6.5 million cases annually and up to 3.8 million associated deaths. Candida albicans is the leading cause of invasive candidiasis, particularly in hospitalized and immunocompromised patients, and is classified as a critically important pathogen by the World Health Organization (WHO). Although traditionally regarded as a human mucosal commensal, C. albicans has been isolated from a wide range of domestic and wild animal species. However, the genetic diversity of wildlife-derived isolates remains poorly explored, despite their potential zoonotic relevance. Investigating intra-specific genetic variability across different hosts is therefore essential within the One Health framework, which emphasizes the interconnectedness of human, animal, and environmental health in the management of infectious diseases and antifungal resistance. To date, animal-derived isolates are severely underrepresented in the international C. albicans PubMLST database, accounting for only 4.5% of the 5,869 deposited strains. This gap limits our understanding of its genetic structure and limits robust evaluation of its epidemiological and zoonotic potential. In this study, 41 C. albicans isolates obtained from Italian wildlife (European hedgehogs, wolves, badgers, foxes, a porcupine, and a roe deer) were genetically characterized using partial amplification of the HWP1 gene and different genotyping approaches, including ABC typing and multilocus sequence typing (MLST). The hwp1 amplification generated the expected 941 bp amplicon in 40 isolates, of which 12 (29.3%) also yielded an additional fragment of approximately 850 bp, indicating heterozygosity at this locus. Isolate IZSUM-7 produced a single amplicon of ~850 bp, which corresponds to a rare homozygous hwp1 pattern recently identified in some Colombian vulvovaginal C. albicans isolates. ABC typing showed that most C. albicans isolates belonged to genotype B (27/41; 65.8%). followed by genotypes A (10/41; 24.4%) and C. isolates (4/41; 9.8%). MLST analysis demonstrated high genetic variability, with a total of 116 alleles identified, including 20 novel alleles, and 36 Diploid Sequence Types (DSTs), of which 28 had not been previously described. Phylogenetic analyses of MLST data showed that animal isolates were distributed across multiple established C. albicans clades (1, 3, 7, 10, 11, 12, 14, 15, and 17) and often clustered with human clinical isolates. Nevertheless, although no definitive evidence for host-specific lineages was found, a certain degree of genetic separation between human and animal isolates was detected by nearest-neighbor analysis, consistent with previous observations reported in other studies. Overall, these findings highlight C. albicans’ ability to circulate across diverse hosts and emphasize the need for One Health–based surveillance to monitor potential zoonotic transmission and emerging antifungal resistance. The Nearest-Neighbour analysis of MLST profiles from both human and animal isolates from Italy (this study and PubMLST data), according previous study (2), revealed host-specific clustering, indicating the absence of distinct genotypic groupings between isolates of different origins. These findings demonstrate high genetic diversity among C. albicans isolates from Italian wildlife, contributing 28 new DSTs and rare genotype C strains to PubMLST. Overall, the data highlight the species’ ability to circulate across hosts without host-adapted lineages and underscore the importance of One Health surveillance to monitor potential zoonotic transmission and antifungal resistance.