PURPOSE OF THE STUDY.
To analyze the relationship between farming, asthma status, and the diversity and composition of bacterial microbiota of mattress dust and nasal swab samples in children.
The study included 86 school-aged children from the Austrian arm of the Genetic and Environmental Causes of Asthma in the European Community–Advanced Studies (GABRIELA) cross-sectional multidisciplinary study.
Mattress dust and nasal samples were collected between May and July 2007. DNA from the samples were analyzed and then clustered together in operational taxonomic units (OTUs), which are defined as clusters of the respective 16S ribosomal RNA sequences with at least 97% sequence similarity. Based on the number of OTUs, bacterial diversity and composition were determined and related to farm exposure and asthma status.
Bacterial diversity in mattress dust was significantly greater in farm children and in those with exposure to cow and straw compared with nonfarm children. In nasal samples, an association with bacterial diversity was seen only with exposure to both cow and straw compared with those with no exposure to either. In mattress dust, Clostridium, Facklamia, an unclassified genus within the family of Ruminococcaceae, and 6 OTUs were significantly associated with farming. Asthma was inversely related with richness and diversity in mattress dust (adjusted odds ratio [aOR] = 0.48 [0.22–1.02]; aOR = 0.41 [0.21–0.83], respectively), and to a lesser extent in nasal samples (aOR = 0.63 [0.38–1.06]; aOR = 0.66 [0.39–1.12], respectively), even after controlling for medication and atopy status.
In this study, it was found that mattress dust and nasal samples in farm children had greater bacterial diversity than in non–farm children. The stronger inverse association of asthma with bacterial diversity in mattress dust as compared with nasal samples suggests microbial involvement beyond mere colonization of the upper airways.
Researchers in numerous previous studies, many of whom are from these same authors, have convincingly shown reduced rates of allergic disease in children growing up on farms. This has been presumed to be related to effects on the microbiome, and this study takes another step forward in demonstrating these relationships. The addition of nasal sampling is especially interesting, with results opposite of those that had been hypothesized because they suggest that colonization of the airways is not the predominant mechanism for asthma protection in farm children.
- Copyright © 2017 by the American Academy of Pediatrics