Increased prevalence and altered species composition of filamentous fungi in respiratory specimens from cystic fibrosis patients

Abstract

Filamentous fungi cultured from respiratory tract specimens submitted to the department of clinical microbiology, Aarhus University Hospital, during 2010 were identified by morphology and by internal transcribed spacer (ITS) sequencing. Of 343 fungal isolates, discrepancies between identification methods were observed for four isolates (1.2%), while identification to species was achieved only with ITS sequencing for 16 isolates (4.7%). Filamentous fungi were isolated from 15% of cystic fibrosis (CF) respiratory samples in contrast to 2% of non-CF samples. From CF patients, a total of nine different species were found in 188 samples from 48 patients, whereas from non-CF patients, 24 different species were found in 155 samples from 111 patients. CF was associated with a significant overrepresentation of Aspergillus fumigatus and Scedosporium species; in contrast, the frequency of Penicillium spp. and other putative contaminants were significantly increased in non-CF patients. The altered species variation of filamentous fungi in CF respiratory specimens is contradictory to a scenario of incidentally inhaled spores, trapped in the viscous airway mucus of these patients and subsequently expectorated; rather, our data most likely reflect both an increased prevalence and an increased proportion of truly colonizing fungi in this patient group.