Fungal and bacterial species, endotoxin, and inflammatory potential of airborne settled dust from homes

This study aimed to identify airborne fungal and bacterial species and endotoxin levels in homes, and to assess whether the total inflammatory potential (TIP) was associated with microbial levels, specific species, and self-reported mould (hereafter classified as mouldy). Airborne settling dust was collected in 227 homes using electrostatic dust collectors over 14 days. Microorganisms were identified using MALDI-TOF MS. The TIP of the samples was analysed using a human cell line. Concentrations of fungi, endotoxin, and TIP were associated with season. Based on questionnaire data, 12% of the homes were categorized as mouldy. In these homes, significantly higher fungal concentrations and higher TIP were measured. In total, 91 fungal species were identified, and concentrations of several species were significantly correlated. Of 36 fungal species included in a linear model with season and mould-status as predictors, 23 exhibited seasonal variation and 10 were found at significantly higher concentrations in homes with self-reported mould. In total, 220 bacterial species were identified. In a model including concentrations of fungal species, bacterial genera, and endotoxin, Aspergillus fumigatus, A. ochraceus, and Cladosporium halotolerans remained significantly associated with TIP after backward elimination. Some of the identified fungal species are commonly associated with allergic airway disease, and seven fungal species and 27 bacterial species belong to Risk Class 2. With the identification of 311 different species of microorganisms, systematic differences in fungal species concentrations were observed between seasons and self-reported mould-status, and specific fungal species were associated with higher TIP.