Isolation of filamentous fungi from sputum in asthma is associated with reduced post-bronchodilator FEV ₁

Abstract

Background

Fungal sensitization is common in severe asthma, but the clinical relevance of this and the relationship with airway colonization by fungi remain unclear. The range of fungi that may colonize the airways in asthma is unknown.

Objective

To provide a comprehensive analysis on the range of filamentous fungi isolated in sputum from people with asthma and report the relationship with their clinico-immunological features of their disease.

Methods

We recruited 126 subjects with a diagnosis of asthma, 94% with moderate-severe disease, and 18 healthy volunteers. At a single stable visit, subjects underwent spirometry; sputum fungal culture and a sputum cell differential count; skin prick testing to both common aeroallergens and an extended fungal panel; specific IgE to Aspergillus fumigatus. Fungi were identified by morphology and species identity was confirmed by sequencing. Four patients had allergic bronchopulmonary aspergillosis.

Results

Forty-eight percent of asthma subjects were IgE-sensitized to one fungal allergen and 22% to ≥ 2. Twenty-seven different taxa of filamentous fungi were isolated from 54% of their sputa, more than one species being detected in 17%. This compared with 3 (17%) healthy controls culturing any fungus ( P < 0.01). Aspergillus species were most frequently cultured in isolation followed by Penicillium species. Post-bronchodilator FEV ₁ (% predicted) in the subjects with asthma was 71(± 25) in those with a positive fungal culture vs. 83 (± 25) in those culture-negative, ( P < 0.01).

Conclusion and Clinical Relevance

Numerous thermotolerant fungi other than A. fumigatus can be cultured from sputum of people with moderate-to-severe asthma; a positive culture is associated with an impaired post-bronchodilator FEV ₁, which might be partly responsible for the development of fixed airflow obstruction in asthma. Sensitization to these fungi is also common.