Eco-phenotypic characterization of Candida palmioleophila from poultry litter and marine environments: implications for One Health.

Candida palmioleophila is an emerging opportunistic yeast frequently misidentified within the Meyerozyma guilliermondii complex, potentially obscuring its clinical and ecological relevance. Although its clinical significance is increasingly recognized, the phenotypic characteristics of environmental isolates remain poorly explored. This study evaluated the eco-phenotypic profiles of 14 C. palmioleophila isolates recovered from two anthropogenically influenced environmental sources: poultry litter (n = 6) and urbanized coastal environments (n = 8). Antifungal susceptibility testing revealed high fluconazole MICs among all evaluated isolates (32 to > 128 µg/mL), while amphotericin B, caspofungin, and anidulafungin MICs ranged from 1 to 2 µg/mL, 0.25 to 1 µg/mL, and 0.06 to 0.5 µg/mL, respectively. No detectable association was observed between variation in antifungal MICs and biofilm biomass under the tested conditions. The isolates exhibited broad physiological tolerance, including growth at temperatures up to 40 °C, tolerance to high NaCl concentrations and cell-wall stress, as well as variation in cell-wall chitin content and intracellular lipid-body accumulation. Virulence-associated phenotypes included biofilm formation, high cell-surface hydrophobicity in most isolates, widespread esterase activity, variable phospholipase activity, and limited protease activity. Together, these findings expand current knowledge of the environmental phenotypic repertoire of C. palmioleophila and support broader environmental, clinical, and genomic surveillance to clarify its ecology, population structure, and potential transmission pathways.