Real-Time PCR Detection of the Basidiomycetous Fungus Bjerkandera adusta: A Tool to Identify Itraconazole Responder Patients with Unexplained Chronic Cough.

ABSTRACT

BACKGROUND: Filamentous basidiomycetes (f-BMs) are involved in some unexplained chronic cough (UCC) cases that can be improved by the administration of antifungal agents. The disease concept was termed fungus-associated chronic cough (FACC). The current diagnostic criteria warrant environmental fungi isolation from respiratory specimens, which is hardly conceivable for such fungi. OBJECTIVES: This study aimed to detect the f-BMs Bjerkandera adusta, the most common pathogen in FACC, from respiratory specimens of patients with UCC using real-time polymerase chain reaction (PCR). It also evaluated the applicability of the PCR system to detect antifungal agent responders among patients with unexplained cough. METHODS: The PCR system specific to B. adusta was developed and its utility was evaluated using sputum samples from 23 patients with chronic cough. RESULTS: B. adusta was detected in 10 out of 14 patients with UCC (71.4%), in contrast to only 2 out of 9 patients with non-UCC (22.2%; p < 0.05 with the Fisher's exact test). The copy number of the samples correlated with the therapeutic impact score for cough symptoms following the oral administration of itraconazole. CONCLUSION: Development of the real-time PCR system enabled us to demonstrate that many patients with UCC might be influenced by B. adusta, a fact evidenced by the improvement of symptoms with itraconazole administration in most PCR-positive patients. This method would help in detecting itraconazole responders among patients with UCC when the isolation of f-BMs is not achievable.