PFGE-Based Epidemiological Study of an Outbreak of Candida tropicalis Candiduria: The Importance of Medical Waste as a Reservoir of Nosocomial Infection

Between November 2002 and March 2003, an outbreak of candiduria occurred in the surgical intensive care unit (SICU) of a university-affiliated hospital in South Korea. This outbreak affected 34 patients and was caused by Candida tropicalis. To determine the source of the epidemic and the risk factors, surveillance cultures from the SICU, genotyping of Candida isolates by pulsed-field gel electrophoresis (PFGE), and a case-control study were performed. The surveillance cultures revealed that 6 environmental samples related to the urine disposal route were positive for C. tropicalis. The PFGE analysis of genomic DNA demonstrated identical band patterns for all of the C. tropicalis isolates obtained from SICU patients and the 6 environmental samples during the outbreak period, while epidemiologically unrelated strains showed unique PFGE band patterns. Although no risk factors were identified by the case-control study, this epidemiological investigation involving the use of molecular techniques suggests that improper disposal of infectious medical waste led to the cross-transmission of a single clone that was responsible for the outbreak of C. tropicalis candiduria in this SICU. After implementing a better urine disposal system and thorough hand washing procedures, no further clusters of candiduria were detected in the SICU.