Fecal Bacteroides are linked to bronchiolitis

Investigators identified 4 distinct fecal microbiota profiles in infants hospitalized with bronchiolitis and found that 1 of those profiles-dominated by Bacteroides-was associated with a higher likelihood of bronchiolitis than the others.

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The case control study was conducted in 40 infants aged younger than 12 months who were hospitalized for bronchiolitis in 1 of 3 facilities, and 115 healthy infants. Median age overall was 3 months. Investigators collected fecal samples from all participants and used gene sequencing to determine the relative abundance of various organisms. In addition to the Bacteroides-dominant profile, they identified profiles dominated by the following organisms: Escherichia; Bifidobacterium, and Enterobacter/Veillonella.

The proportion of infants with severe bronchiolitis was lowest (15%) in the Enterobacter/Veillonella-dominant profile compared with highest (44%) in the Bacteroides-dominant profile-a significant difference. However, the likelihood of bronchiolitis in infants with the Escherichia-dominant or Bifidobacterium-dominant profile was not significantly different than in those with the Enterobacter/Veillonella-dominant profile. These findings persisted after adjustment for variables (Hasegawa K, et al. Pediatrics. 2016;138[1]:e20160218).

Commentary Investigators are making more and more interesting observations on the microbiome. In this case, it is not clear if variation in the fecal flora causes more severe respiratory viral infections and bronchiolitis. However, the researchers suggest that gut microbiota dominated by certain bacteria, in this case Bacteroides, “attenuates the development of the immune function in the respiratory tract and thereby leads to an increased susceptibility to bronchiolitis.” They cite other studies to support this theory. We still have lots to learn about how we interact with organisms on us and in us. -Michael G Burke, MD

Ms Freedman is a freelance medical editor and writer in New Jersey. Dr Burke, section editor for Journal Club, is chairman of the Department of Pediatrics at Saint Agnes Hospital, Baltimore, Maryland. The editors have nothing to disclose in regard to affiliations with or financial interests in any organizations that may have an interest in any part of this article.