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June 22nd: Gut microbes, allergic disease and hygiene – is there a link?

A new paper reviews studies of the role of gut microbiota in allergic diseases and asthma.  The data provides further evidence that a disturbed gut microbiota is associated with increased risk of allergic disease, and that changing the gut microbiota by dietary means (high fiber/acetate or prebiotics) in pregnancy may reduce the risk of allergic airways disease and food allergy in the offspring.

Although candidate bacterial species have been reported it still remains unclear which bacteria (or other microbes), in which numbers and combinations, and when during the gut colonization process may prevent allergic diseases and asthma. Data show that the first intestinal colonizers of a baby are derived from the mother before and during delivery and there is emerging evidence of an early-life ‘critical window’, when the effects of gut microbial dysbiosis are most influential in immune development. From this the authors conclude that, in humans, early-life exposures including delivery mode, perinatal treatment with antimicrobials, infant feeding, and the general environment have the capacity to influence the microbiome composition and disease risk. Vaginally delivered infants are primarily colonized by a microbiome enriched for Escherichia coli/Shigella, Bacteroides, and Bifidobacterium, whereas cesarean-section born infants, who appear to be at higher risk of allergic diseases and asthma, are typically colonized with skin bacteria, such as Staphylococcus and Corynebacterium and have delayed colonization with Bacteroides. Recent studies report that the oral, skin, and anal microbiota of cesarean-section born infants could be partly restored by transfer of maternal vaginal microbes at birth.

Although the paper cites “hygiene” as a factor which affects the cross talk between the neonate and its environment, it cites no data as to whether, or to what extent, hygiene measures designed to protect the neonate from infectious disease before the developing immune system becomes competent, might contribute to dysregulation of the host–microbe relationship appears in a way which might cause of inflammation and disease development.

Simonyte SK, Vidman L, Rydén P, West CE. Emerging evidence of the role of gut microbiota in the development of allergic diseases. Current opinion in allergy and clinical immunology. 2016 May. The paper can be found at: http://europepmc.org/abstract/med/27253486