Silent Persistence: Molecular Evidence of Clonal Transmission in Fluconazole-Resistant Candida parapsilosis Hospital Outbreaks over Decades

Fluconazole-resistant Candida parapsilosis has emerged as a significant nosocomial pathogen, contributing to extensive outbreaks with severe clinical implications. Despite increasing evidence of clonal transmission, the genetic mechanisms that facilitate the persistence of hospital reservoirs remain inadequately characterized. We aimed to characterise the long-term molecular epidemiology of fluconazole-resistant Candida parapsilosis bloodstream isolates (n = 47) collected between 1997 and 2019 at a tertiary centre. All isolates underwent microsatellite analysis using three polymorphic markers (CP1, CP4, B5). Genetic diversity, temporal distribution, and clonal relationships were assessed through phylogenetic analysis and discriminatory power calculations. Microsatellite analysis revealed minimal genetic diversity (combined discriminatory power: 0.7114), with only six distinct genotypes identified. Two dominant clones (Genotype-1: 23.4%, Genotype-2: 46.8%) persisted throughout the study, showing apparent spatiotemporal clustering in surgical and intensive care units. Phylogenetic analysis demonstrated tight genetic clustering, consistent with prolonged clonal persistence across multiple years and clinical departments. Our findings provide strong molecular evidence consistent with persistent, multi-year clonal transmission; however, definitive confirmation will require higher-resolution genomics and epidemiologic linkage. These results underscore the need to strengthen infection-control practices to curtail sustained clonal persistence within the hospital.