Isolation of fungi, especially Exophiala dermatitidis, in patients suffering from cystic fibrosis. A prospective study.

Patients with cystic fibrosis (CF) are at an increased risk of pulmonary colonisation by opportunistic micro-organisms. Using specialised methods, the black yeast Exophiala dermatitidis could consistently be cultured from CF patients. Isolation rates from sputum samples ranged between 1.8 and 15.7%. Occasionally, infection could be recognised. This study aimed at investigating the isolation rates of E. dermatitidis in samples taken from CF patients at the University of Bonn, Germany. Altogether, 439 respiratory specimens taken from 81 CF patients were screened for the occurrence of E. dermatitidis over a period of 18 months. For the selective isolation of this fungus erythritol-chloramphenicol agar (ECA) produced in house was applied. The isolation rate of E. dermatitidis was 1.1% from all specimens, 1.6% from all sputum samples and 6.2% in all patients examined. Prior to the introduction of ECA, E. dermatitidis had never been isolated in our laboratory, either from CF, or from any other patient. During this study, E. dermatitidis was found to colonise the respiratory tract of some CF patients. The use of additional selective culture media is necessary for the recognition of uncommon fungi, e.g. E. dermatitidis, in CF patients.