Detection of Filamentous Fungi in the Homes and Airways of Patients with Asthma

Asthma is a heterogeneous condition characterised by variable airflow obstruction, airway inflammation and hyper-responsiveness. Fungal sensitisation has been associated with asthma severity; and airways colonisation by the pathogenic fungus Aspergillus fumigatus has been associated with a progressive lung function decline in allergic bronchopulmonary aspergillosis. Interest in the home environment as a source of fungal exposure is increasing; however, there are still no accepted guidelines or standardised methods for the quantification of indoor fungal levels. We sought to i) investigate typical airborne fungal spore concentrations in homes and to compare exposure levels in asthma patients grouped according to either A. fumigatus sensitisation or sputum culture; ii) fully characterise the fungal biota capable of colonising the airways in patients with asthma; and iii) define the clinical characteristics of fungal colonisation. Aspergillus/Penicillium-type conidia exhibited indoor predominance and independence of season, and were highest in old, terraced, non-insulated properties. A. fumigatus was the predominant fungus isolated from sputum and IgE sensitisation to A. fumigatus was associated with reduced post-bronchodilator FEV1 in patients with asthma. Sputum culture of filamentous fungi was also associated with reduced lung function, with predominant fungi comprising Aspergillus and Penicillium species; notably Penicillium piceum and species of Aspergillus section Nigri. Higher levels of airborne A. fumigatus were detected in homes of asthmatics with a positive sputum culture for A. fumigatus. In conclusion, sensitisation to A. fumigatus and airways colonisation by fungi are associated with reduced lung function in moderate to severe asthma; and this study provides a direct link between home exposure and airways colonisation.