Researchers pinpoint specific farm bacteria that shield rural children from asthma and allergies

An interdisciplinary team examined bacterial DNA from mattress dust of over a thousand children in southern Germany and compared it with air samples collected from dozens of local farms. The analysis revealed that a specific consortium of nine Gram-positive bacterial genera, notably Romboutsia timonensis and Glutamicibacter arilaitensis, were present at roughly 25% in barn air but only about 6% in bedroom dust. Bioinformatician Giulia Pagani explained that these microbes likely account for two-thirds of the protective effect against asthma and half of the effect against hay fever and atopic eczema.

The bacteria are released from cattle via feces, become airborne in barns, and are inhaled by children, where their metabolites such as tryptophan and linoleic acid engage human AhR and PPAR-γ receptors to dampen inflammation. Epidemiologist Markus Ege highlighted the identified causal chain from microbes to metabolites to immune receptors. An independent replication using the European Pasture cohort of French and Finnish children confirmed the association. The authors note that the cross-sectional design limits causal inference and that direct measurement of bacterial exposure in children’s beds remains lacking.