Three Years of Epidemiological Surveillance of Candida in a Romanian Pulmonology Hospital Reveal an Increase in Fluconazole-Resistant Non-Albicans Species: A One-Centre Retrospective Study

Background: Candida species are among the most frequently isolated fungi from respiratory specimens in hospitalised patients, yet the clinical significance of their presence—infection versus colonisation, treatment versus observation—remains an unresolved challenge in clinical microbiology. Data from dedicated pulmonology centres in Eastern Europe are scarce. This study aimed to characterise the three-year epidemiology, species distribution, temporal trends, colony-load profiles, and longitudinal mycological trajectories of fungal respiratory isolates at a Romanian tertiary pulmonology hospital. Methods: We retrospectively analysed 1000 microbiological records from bronchial aspirates and other respiratory specimens collected between January 2022 and December 2024. Variables included patient demographics, clinical ward, primary diagnosis, fungal species, and semi-quantitative colony counts. Patients with multiple records were identified and analysed as a longitudinal sub-cohort. Results: Candida albicans predominated (45.5%), with a declining proportional trend across the study period. Candida krusei—intrinsically resistant to fluconazole—increased from 5.3% of isolates in 2022 to 9.7% in 2024. The intensive care unit (ICU) accounted for 25.8% of all records. Patients were predominantly male (67.5%) with a mean age of 63.4 years; acute respiratory failure was the most frequent underlying diagnosis (41.7%). High-load colonisation (>100 colony-forming units/mL) was documented in 19.0% of quantified specimens. Among 91 patients with serial cultures, 26 demonstrated inter-sample species shifts—several consistent with antifungal selection pressure—and 29 showed escalating colony loads, suggesting progression from colonisation toward probable infection. Conclusions: In a clinical setting where fluconazole has historically served as the default empirical antifungal agent, a C. krusei proportion approaching 10% of annual isolates constitutes a clinically actionable finding. Species-level identification of all fungal respiratory isolates is strongly warranted, as it directly influences therapeutic decision-making in approximately one in ten cases.