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

Background: 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. Objective: We aimed to determine the extent of clonal spread and persistence patterns of fluconazole-resistant Candida parapsilosis strains across a 22-year period in a tertiary care hospital, using high-resolution microsatellite genotyping. Methods: Forty-seven fluconazole-resistant Candida parapsilosis isolates from candidemia patients (1997-2019) 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. Results: 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, confirming prolonged clonal persistence spanning multiple years and clinical departments. Conclusion: Our findings provide compelling molecular evidence for persistent, multi-year clonal transmission of fluconazole-resistant Candida parapsilosis within hospital environments. These results challenge current infection control paradigms and highlight the urgent need for enhanced surveillance strategies and targeted interventions to interrupt these persistent transmission chains.