Scientists have identified a “missing microbe” that is often absent in babies from western countries and raises the prospect that lifestyle changes are altering the make-up of gut bacteria crucial to health.
The dwindling presence of B. infantis is revealed in a new global atlas of digestive tract bugs. The research is part of a growing effort to understand how the microbiome shapes critical aspects of wellbeing, such as the development of the body’s defences against infection.
It is a “striking example” of how modern lifestyles may reshape the microbiome from birth, said Trevor Lawley, co-senior author of the work and a researcher at the UK’s Wellcome Sanger Institute. “As infant microbiomes influence a child’s development in various ways, such as shaping their immune system, we need to know more about the potential impact of this and whether it could have effects on children’s health.”
The paper published in the journal Cell on Wednesday genetically mapped more than 4,000 strains of two gut bacteria in young children from 48 countries, making it much wider-ranging than previous studies of its kind. The researchers found that B. infantis was much less common in babies from Europe and North America than in African and South Asian countries.
During the first two months of life, B. infantis is absent in about 98.6 per cent of infants in Europe and the US, compared with about 29 per cent in South Asia and Africa, the researchers found. It remains missing over the following months in more than half of the babies in western countries.
B. infantis is an early-arriving so-called pioneer microbe among the gut bugs that help digest foods and train the immune system to distinguish between “good bacteria” and pathogenic threats. Its strains take on regional variations, such as carrying genes in West African children linked to breaking down the staple millet grain fonio, the researchers found.
A shortage of B. infantis could hinder the immune system’s development and explain rising rates in western countries of allergies and so-called autoimmune diseases, in which the body’s defences turn on itself.
Scientists suspect the depleted presence of B. infantis could be linked to trends such as greater antibiotic use, dietary shifts and less exposure to environmental microbes due to improved sanitation.
Shorter breastfeeding periods and the greater use of formula milk could play a big part, said Professor Alan Walker, a University of Aberdeen microbiologist specialising in gastrointestinal bacteria. This would mean there were fewer opportunities for bacteria to pass from mother to child.
“Exclusive or predominant breastfeeding is often less prevalent, and often also occurs for a shorter length of time, in North America and Europe compared to South Asia and Africa,” Walker said.
The research has potential lessons for the so-called bugs as drugs approach, or the therapeutic use of microbes to prevent and treat diseases.
The global gut bacteria atlas scientists discovered that the B. infantis strains they identified were different from those found in commercial probiotic products for young children. This raised doubts about whether those products — typically drops containing gut microbes — were suitable, they said.
“Microbiomes are complex, highly individual ecosystems, yet for decades the infant probiotics industry has taken a one-size-fits-all approach, trying to plant the same bacterial ‘seeds’ in every baby worldwide,” said Yan Shao, the paper’s first author and a Wellcome Sanger Institute researcher.
The research underscores how “local ecological and cultural contexts” shape infant microbiome development and demand “tailored probiotic strategies”, said Cristina Menni, senior lecturer in molecular epidemiology at King’s College London.