Genetica e Genomica di Candida albicans nel concetto One Health

Invasive fungal infections represent a growing threat to global public health, affecting approximately 6.5 million people annually and causing up to 3.8 million deaths. Among fungal pathogens, Candida albicans is one of the most frequently isolated species in clinical settings, responsible for cutaneous and systemic candidiasis, especially in immunocompromised patients. Due to its clinical relevance, C. albicans was included by the World Health Organization in the “WHO Fungal Priority Pathogens List” (2022) as a critically prioritized pathogen. Although traditionally considered a commensal of the human mucosa, C. albicans has also been isolated from numerous animal species, both domestic and wild. However, knowledge of the genetic diversity of isolates from wildlife remains limited, despite increasing interest in their potential zoonotic role. In this context, it is essential to explore the intra-specific and inter-host genetic variability of C. albicans, especially within the One Health concept, which highlights the interconnection between human, animal, and environmental health in the management of infectious diseases and antimicrobial resistance. To date, animal-derived isolates are severely underrepresented in the international PubMLST database dedicated to C. albicans, comprising only 4.9% of animal strains out of a total of 5,786. This gap limits the understanding of the genetic structure and potential epidemiological and zoonotic implications of the species. In this study, 41 C. albicans isolates from Italian wildlife (European hedgehogs, wolves, badgers, foxes, a porcupine, and a roe deer) were analyzed. Isolates were identified using phenotypic tests, MALDI-ToF spectrometry, and partial amplification of the hwp1 gene. Subsequently, isolates were characterized by ABC Typing and Multi-Locus Sequence Typing (MLST). ABC Typing revealed a predominance of genotype B (27 isolates), followed by genotypes A (10) and C (4), the latter rarely detected among C. albicans isolates. MLST analysis showed high genetic variability, with the identification of 116 total alleles, including 20 novel ones, and 36 Diploid Sequence Types (DSTs), 28 of which had never been previously described, substantially expanding the representation of animal isolates in the global database. Phylogenetic analyses placed the isolates within several well-known clades of the global C. albicans phylogeny (mainly clades 11, 1, 14, and 15), with no clear correlation between genotype, host species, or geographical area. No lineages exclusive to wildlife were identified, but some genotypes overlapped with those of human clinical strains, suggesting interspecific genetic flows and a possible transient role of wildlife as a reservoir of potentially pathogenic variants. Overall, the results support a dynamic model of genetic exchange between different environments and species, in accordance with the One Health concept, reinforcing the need to adopt interdisciplinary strategies for molecular surveillance and containment of C. albicans, with the aim of preventing emerging fungal infections and limiting the spread of resistant strains.