Indoor Airborne Microbiome and Endotoxin: Meteorological Events and Occupant Characteristics Are Important Determinants

Minimal research exists onthe factors influencing the indoorbacterial community. Despite their proposed importance for health,here we report environmental factors influencing the composition ofthe indoor bacterial communities. Airborne bacteria and endotoxin may affect asthma andallergies.However, there is limited understanding of the environmental determinantsthat influence them. This study investigated the airborne microbiomesin the homes of 1038 participants from five cities in Northern Europe:Aarhus, Bergen, Reykjavik, Tartu, and Uppsala. Airborne dust particleswere sampled with electrostatic dust fall collectors (EDCs) from theparticipants' bedrooms. The dust washed from the EDCs'clothes was used to extract DNA and endotoxin. The DNA extracts wereused for quantitative polymerase chain (qPCR) measurement and 16SrRNA gene sequencing, while endotoxin was measured using the kineticchromogenic limulus amoebocyte lysate (LAL) assay. The results showedthat households in Tartu and Aarhus had a higher bacterial load anddiversity than those in Bergen and Reykjavik, possibly due to elevatedconcentrations of outdoor bacterial taxa associated with low precipitationand high wind speeds. Bergen-Tartu had the highest difference (ANOSIM R = 0.203) in & beta; diversity. Multivariate regressionmodels showed that & alpha; diversity indices and bacterial and endotoxinloads were positively associated with the occupants' age, numberof occupants, cleaning frequency, presence of dogs, and age of thehouse. Further studies are needed to understand how meteorologicalfactors influence the indoor bacterial community in light of climatechange.