Recognition of a Pseudo-Outbreak of Cladosporium Species by Continuous Monitoring of Culture Results

Yoo, Soohun; Kim, Myung Sook; Chung, Hae Sun; Lee, Yangsoon; Yong, Dongeun; Jeong, Seok Hoon; Lee, Kyungwon; Chong, Yunsop

Abstract

BACKGROUND
Cladosporium spp. are dematiaceous fungi that are commonly isolated from indoor and outdoor environments, including hospital air. This fungus is rarely pathogenic to humans, but has been reported to cause infections of the skin and toenails, as well as sinusitis and pulmonary infections. The monitoring of culture results was conducted to identify the outbreak of an unknown black fungal infection between January and March 2006 in a University hospital, and infection control activity was performed to identify the cause of the outbreak.
METHODS
An epidemiological investigation of 22 patients with infections caused by an unknown black fungus was conducted. Microscopic examination and molecular analysis on the internal transcript spacer (ITS) region was performed to identify the black fungus. To detect the source of contamination, a culture of environmental specimens was performed, and then, disinfection of the laboratory was implemented.
RESULTS
The patients with black fungi belonged to various departments and wards. No symptoms of fungal infection were recognized on the basis of the survey. The black fungus was identified as Cladosporium spp. on the basis of morphological features and ITS region sequencing. Culturing of environmental specimens was performed in the laboratory. Black fungi were isolated from a specimen from a rack and had the same morphological features with Cladosporium spp. from clinical specimens. After the rack was autoclaved, Cladosporium spp. from clinical specimens was no longer isolated.
CONCLUSION
Epidemiological investigation, microscopic examination, and molecular analysis revealed that the sudden increase in the isolation rate of Cladosporium spp. from clinical specimens was the result of a pseudo-outbreak caused by the contamination of a rack. To our knowledge, this is the first report of a pseudo-outbreak of Cladosporium spp. Continuous monitoring of culture results is important to avoid unnecessary labor for nosocomial infection control.