Science

Anne M. Karvonen, PhD, Pirkka V. Kirjavainen, PhD, Martin Täubel, PhD, Balamuralikrishna Jayaprakash, MSc, Rachel I. Adams, PhD, Joanne E. Sordillo, ScD, Diane R. Gold, MD, MPH, Anne Hyvärinen, PhD, Sami Remes, MD, MPH, Erika von Mutius, MD, and Juha Pekkanen, MD

BACKGROUND:
Early-life indoor bacterial exposure is associated with the risk of asthma, but the roles of specific bacterial genera are poorly understood.
OBJECTIVE:
We sought to determine whether individual bacterial genera in indoor microbiota predict the development of asthma.
METHODS:
Dust samples from living rooms were collected at 2 months of age. The dust microbiota was characterized by using Illumina MiSeq sequencing amplicons of the bacterial 16S ribosomal RNA gene. Children (n = 373) were followed up for ever asthma until the age of 10.5 years.
RESULTS:
Richness was inversely associated with asthma after adjustments (P = .03). The phylogenetic microbiota composition in asthmatics patients’ homes was characteristically different from that in nonasthmatic subjects’ homes (P = .02, weighted UniFrac, adjusted association, permutational multivariate analysis of variance, PERMANOVA-S). The first 2 axis scores of principal coordinate analysis of the weighted UniFrac distance matrix were inversely associated with asthma. Of 658 genera detected in the dust samples, the relative abundances of 41 genera correlated (r greater than |0.4|) with one of these axes. Lactococcus genus was a risk factor for asthma (adjusted odds ratio, 1.36 [95% CI, 1.13-1.63] per interquartile range change). The abundance of 12 bacterial genera (mostly from the Actinomycetales order) was associated with lower asthma risk (P less than .10), although not independently of each other. The sum relative abundance of these 12 intercorrelated genera was significantly protective and explained the majority of the association of richness with less asthma.
CONCLUSION:
Our data confirm that phylogenetic differences in the microbiota of infants’ homes are associated with subsequent asthma risk and suggest that communities of selected bacteria are more strongly linked to asthma protection than individual bacterial taxa or mere richness.