A follow-up study was conducted when the 47 participating infants reached their seventh birthday. By then eight of them – 17% – were suffering from chronic asthma. 28% had hay fever, 26% still had eczema, and 34% reacted to the allergens in a skin prick test. But it was only the asthma cases that could be connected to low intestinal microbial diversity at the age of one week and one month, according to the results now being published in the scientific journal Clinical & Experimental Allergy.
“A high diversity of gut microbiota during the first months of life seems to be important for the maturation of the immune system,” says Thomas Abrahamsson, paediatrician and researcher at Linköping University, and principal author of the article.
The hypothesis is that in order to function effectively, the immune system needs to be “trained” by large numbers of different microorganisms. In the absence of sufficient stimulation from large numbers of different bacteria, the system may overreact to innocuous antigens it encounters.
Strengthen the barrier function
A high gut microbial diversity has also been shown to strengthen the barrier function of the mucous membrane.
“We are speculating that a deficient maturity of the immune system at an earlier age and a less efficient mucosa barrier function can open the way to certain types of viral infection that can be linked to the development of asthma,” says senior author Maria Jenmalm, professor of experimental allergology.
The analysis of the bacteria flora in the children's stools was carried out using a method known as 454 pyro sequencing at the Science for Life Laboratory, in conjunction with researchers Anders Andersson and Lars Engstrand. This is a powerful genetic method that identifies DNA sequences typical of different bacterial species, including those that cannot be cultivated in the traditional way.
Article: Low gut microbiota diversity in early infancy precedes asthma at school age by T Abrahamsson, H Jakobsson, A F Andersson, B Björkstén, L Engstrand and M C Jenmalm. Clinical & Experimental Allergy, in print 2014.