Corticosteroid treatment is associated with increased filamentous fungal burden in allergic fungal disease

BACKGROUND: Allergic diseases caused by fungi are common. The best understood conditions are allergic bronchopulmonary aspergillosis and severe asthma with fungal sensitization. Our knowledge of the fungal microbiome (mycobiome) is limited to a few studies involving healthy individuals, asthmatics, and smokers. No study has yet examined the mycobiome in fungal lung disease.

OBJECTIVES: The main aim of this study was to determine the mycobiome in lungs of individuals with well-characterized fungal disease. A secondary objective was to determine possible effects of treatment on the mycobiome.

METHODS: After bronchoscopy, ribosomal internal transcribed spacer region 1 DNA was amplified and sequenced and fungal load determined by real-time PCR. Clinical and treatment variables were correlated with the main species identified. Bronchopulmonary aspergillosis (n = 16), severe asthma with fungal sensitization (n = 16), severe asthma not sensitized to fungi (n = 9), mild asthma patients (n = 7), and 10 healthy control subjects were studied.

RESULTS: The mycobiome was highly varied with severe asthmatics carrying higher loads of fungus. Healthy individuals had low fungal loads, mostly poorly characterized Malasezziales. The most common fungus in asthmatics was Aspergillus fumigatus complex and this taxon accounted for the increased burden of fungus in the high-level samples. Corticosteroid treatment was significantly associated with increased fungal load (P < .01).

CONCLUSIONS: The mycobiome is highly variable. Highest loads of fungus are observed in severe asthmatics and the most common fungus is Aspergillus fumigatus complex. Individuals receiving steroid therapy had significantly higher levels of Aspergillus and total fungus in their bronchoalveolar lavage.