Abstract

Background: Trichosporon asahii is an emerging opportunistic yeast of growing concern in nosocomial settings, particularly in immunocompromised critically ill patients. Outbreaks in intensive care units remain infrequently reported, and environmental reservoirs are seldom fully characterized. Methods: A prospective outbreak investigation was conducted from 16 August to 29 October 2024 at a 496-bed high-complexity university hospital in Cali, Colombia. Case definitions distinguished healthcare-associated infection (HCAI) from colonization. Active surveillance included clinical cultures, environmental sampling of surfaces, biomedical equipment, and air conditioning duct systems. Microbiological identification was performed using MALDI-ToF mass spectrometry. Results: Nine cases were identified among 74 patients (6.76% attack rate); five were HCAIs, and four were colonizations. Overall mortality was 44%, though 0% was attributable to T. asahii. Primary risk factors included prolonged hospitalization, invasive devices, and broad-spectrum antibiotics. While environmental cultures were negative, maintenance records revealed unscheduled air duct cleaning and intermittent AC failures in the affected unit. Conclusions: Epidemiological evidence suggests that air conditioning malfunctions and temperature fluctuations facilitated fungal dispersal. The outbreak was contained through unit closure, hydrogen peroxide vaporization, and reinforced hand hygiene, highlighting the necessity of rigorous ventilation maintenance in high-complexity units.

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