Lack of standardization in the procedures for mycological examination of sputum samples from CF patients: a possible cause for variations in the prevalence of filamentous fungi

Abstract

Filamentous fungi and yeasts are increasingly isolated from respiratory secretions of patients with cystic fibrosis (CF), and persistent fungal colonization of the airways of such patients is thought to exacerbate lung damage. While many independent studies have identified Aspergillus fumigatus complex as the principal colonizing fungus in CF, increased awareness of the role of fungi in CF pathology coupled with improved mycological culture and identification methods have resulted in a number of other fungi being isolated and reported from CF sputum samples, including A. terreus, members of the Pseudallescheria boydii/Scedosporium apiospermum complex, Exophiala dermatitidis, Paecilomyces and Penicillium species. However, the range of fungal pathogens isolated and the relative prevalence of individual species vary widely between reports from different geographical CF centres, and as yet no standardized method for the mycological examination of CF sputum samples has been adopted. Here, we examine the potential contribution of the mycological methods employed to examine CF respiratory secretions relative to the variability in the fungal biota reported. The role of direct microscopic examination of respiratory samples and the impact of the culture conditions used on the detection of specific fungal pathogens are addressed, and the potential significance of isolation of yeast species from CF patient airways is discussed.

Aspergillus Species and Other Molds in Respiratory Samples from Patients with Cystic Fibrosis: a Laboratory-Based Study with Focus on Aspergillus fumigatus Azole Resistance

“…Other fungi, such as Scedosporium spp., Exophiala dermatitidis, Acrophialophora fusispora, and recently Geosmithia argillacea, have also been detected (6,13,14,25). However, reported rates are influenced by both laboratory-and patient-related factors, e.g., type of culture media used, incubation time, age of patients, applied definitions of transient or persistent mold colonization, and sampling frequencies (8,32).…”

Purification and Characterization of a Mycelial Catalase from Scedosporium boydii, a Useful Tool for Specific Antibody Detection in Patients with Cystic Fibrosis

“…Highly specific monoclonal antibodies which might allow the immunodetection of the fungus have been described by Thornton (18), but they are not commercially available. As for mycological examination, it requires skill and expertise and may lead to false-negative results for polymicrobial specimens like sputum samples because of the more rapid and more extensive growth of other molds frequently associated with this fungus, like Aspergillus fumigatus (19). Several molecular methods have been proposed for detection of the fungus from sputum samples (20)(21)(22)(23)(24), but as culture methods, they do not allow the differentiation between airway colonization and sensitization of the patient or respiratory infection in the CF context, which has important implications for patient management.…”

Prospective Multicenter Study of Pneumocystis jirovecii Colonization among Cystic Fibrosis Patients in France

“…Each specimen examined was considered an independent event since the delay between two sputum sample collections was at least 6 months (18). Samples were collected and analyzed according to a standardized protocol as previously described (3,8).…”