Resistant Candida spp. in Healthy Individuals: Mapping a Surveillance Blind Spot

The prevalence and characteristics of resistant, biofilm-forming Candida strains in healthy individuals remain poorly understood. In this work, Candida strains from 23 healthy volunteers and 11 candidiasis patients (n = 34) were isolated and characterized. Biofilm formation capacity, matrix composition, and antifungal susceptibility to common drugs (fluconazole, voriconazole, anidulafungin, amphotericin B) were determined. Overall, C. albicans was the predominant species (77%), but non-Candida albicans Candida species were more frequent in clinical infections (45% vs. 11%). Seventy percent of isolates from healthy asymptomatic individuals confirmed resistance to at least one antifungal agent, with only 30% remaining fully susceptible. Among candidiasis patients, 100% showed resistance. Biofilm formation was prevalent in both groups (83% healthy, 82% patients), but the ability to form biofilms did not correlate with resistance patterns (r = 0.274, p = 0.1665), suggesting independent mechanisms. Matrix analysis showed that 50% of strains produced protein-poor, polysaccharide-rich biofilms. This study demonstrates that healthy asymptomatic individuals are key reservoirs of substantial populations of resistant, biofilm-forming Candida strains, which represents a previously underappreciated community harbor. These findings demonstrate a critical gap in current resistance surveillance and underscore the need for WHO One Health approaches incorporating community-based sampling.