Isolation of Exophiala dermatitidis is not associated with worse clinical outcomes during acute pulmonary exacerbations in cystic fibrosis

Abstract

Introduction. The black yeast Exophiala dermatitidis has been isolated in respiratory samples from people with cystic fibrosis (CF). However, adequate detection may require longer incubation periods than the current UK national standard for CF respiratory samples. Furthermore, it is unclear whether isolation of E. dermatitidis is associated with poorer clinical outcomes in CF. Hypothesis/gap statement. E. dermatitidis does not cause clinically significant lung disease in CF adults. Aim. To evaluate differences in clinical outcomes over a 12 month period and during acute pulmonary exacerbations between CF adults with and without untreated E. dermatitidis. Methodology. Incubation times for respiratory samples on Sabouraud dextrose agar with chloramphenicol (SABC) plates at a large regional adult CF centre were extended from 2 to 7 days over a 1 month period. The number of patients from whom E. dermatitidis was isolated, and the length of incubation time prior to isolation, were recorded. Outcomes of treatment of exacerbations with intravenous antibiotics but in the absence of concomitant antifungal therapy were compared between those with and without E. dermatitidis, as were changes in lung function and body mass index (BMI) over a 12 month period. Results. Extended incubation unmasked the presence of E. dermatitidis in 22 of 132 patients; all isolations occurred after >48 h of incubation. Patients who isolated E. dermatitidis had lower rates of Pseudomonas aeruginosa isolation (P=0.02) and higher rates of non-tuberculous mycobacteria isolation (P=0.03), and were more likely to be prescribed a long-term antifungal medication (P=0.03), but had no differences in age, sex, baseline lung function or body mass index (BMI). There were no differences in response to treatment of acute exacerbations between patients with and without E. dermatitidis, or in change in forced expiratory volume in 1 s (FEV1), BMI and number of exacerbations over 12 months of follow-up. Conclusion. E. dermatitidis is not associated with worse clinical outcomes in CF. Given potential side effects and drug interactions, routine targeting of E. dermatitidis with antifungals during acute exacerbations is not advised.