Family-based study reveals decreased abundance of sputum Granulicatella in asthmatics.

It has been documented that the airway microbiome differs between asthmatics and healthy individuals. However, the microbial signature associated with asthma remains unclear. One of the major limitations is that the case-control study design used in existing studies may not adequately control for baseline variation in bacterial abundance between individuals. In order to further identify asthma-associated airway microbes, we performed a family-based pilot study. In this study, we investigated the microbiome of induced sputum samples from 14 participants from three two-generational pedigrees. Each pedigree has both asthmatic and non-asthmatic offspring. We compared the differences in the relative abundance of bacteria between asthmatic and non-asthmatic siblings within each family and identified bacterial genus with the same trend across the three families. Our results, for the first time, linked asthma with decreased abundance of sputum Granulicatella and verified the previous finding that Veillonella is increased in the airway of asthmatic subjects. This demonstrates the promise of a family-based study design in the search for a bacterial signature for asthma.