Selective Isolation of Pseudallescheria and Scedosporium Species from Respiratory Tract Specimens of Cystic Fibrosis Patients

Background: Fungi of the Pseudallescheria/Scedosporium complex are known to be colonizers and infectious agents of the respiratory tract of cystic fibrosis (CF) patients. Colonized CF patients are at high risk for the development of disseminated scedosporiosis after lung transplantation. The detection of these fungi may be difficult, because they grow slowly and so will be overgrown by faster-developing microorganisms on the media routinely used in diagnostic laboratories. Objectives: To examine the usefulness of the isolation medium SceSel+ agar as a diagnostic tool for clinical samples from CF patients. Methods: 150 respiratory tract samples from 42 CF patients were inoculated on SceSel+ agar. During the incubation phase, which lasted up to 30 days at 36 8 1 C, the cultures were inspected every 2 or 3 days. Results: The isolation of Scedosporium species was successful in 3 samples (2%) with standard microbiological media and procedures, while the isolation rate on SceSel+ agar was 5.3% (8 of 150 specimens). Conclusions: Our results suggest that standard microbiological media and procedures are not sufficient to detect colonization of the respiratory tract by Pseudallescheria/Scedosporium in CF patients. By use of SceSel+ agar, fungi belonging to this complex were isolated more frequently. Therefore, this semiselective mycological isolation medium should be used for the detection of these fungi in the respiratory tract of CF patients, especially in patients in whom a fungal infection is assumed or who are scheduled for lung transplantation. Copyright (C) 2008 S. Karger AG, Basel