Babies in non-industrialized areas share fewer microorganisms with their mothers

Are children’s microbiomes the same in all parts of the world? It is to this question that an international research group tries to answer, in which the Institute of Agrochemistry and Food Technology (IATA) of the CSIC participates.

In a study published in current biology, the team points out that in non-western countries, such as Ethiopia, children share fewer microorganisms with their mothers than in western countries, such as Sweden and Italy, as a result of less transmission through breast milk. However, Ethiopian children had a greater variety of microorganisms in their microbiome, including some uncharacterized species from the environment and local foods.

In the West, children share more microorganisms with their mothers than in other countries such as Ethiopia

The origin of the human microbiome begins at birth, when the first microorganisms that inhabit our bodies are acquired mainly from the mother. So far, it has been studied how the type of delivery (natural or cesarean section), antibiotic prophylaxis and the method of feeding, especially breastfeeding, modulate the transmission of the microbiome from mother to child.

However, other key factors such as westernized lifestyles, with high sanitation, high calorie diets and urban environments, compared to non-westernized and more rural lifestyles, have yet to be analyzed.

The research had more than 700 genomic samples from children and their mothers

Now, an international research team, co-led by Nicola Segata (University of Trento), Edoardo Pasolli (University of Naples) and María Carmen Collado (IATA-CSIC), has explored the microbiome exchange between mother and baby, through the metagenomic analysis of more than 700 samples of newborns (under one year old), children up to 12 years old and their mothers, obtained in Ethiopia, comparing them with others from countries such as Ghana and Tanzania, as well as other more industrialized countries such as Italy and Sweden. The Ethiopian samples come from collaboration with Mari Olcina (Universitat de València), MOSSolidaria ONGD and the GeNaPi project team, which includes CSIC and UV staff.

The results of the analysis show that the microbiome composition of Western and non-Western newborns overlapped during the first few months of life more than afterwards, reflecting similar early diets based on breast milk.

“Ethiopian and other non-Western babies shared a smaller fraction of the microbiome with their mothers than most Westernized populations,” reveals María Carmen Collado. Specifically, Ethiopian babies share less than 5% of microorganisms with their mothers (in line with other African countries), compared to 29% shared by Western babies.

Ethiopian and other non-Western babies shared a smaller fraction of the microbiome with their mothers

Maria Carmen Collado

The reason for this difference is unclear to researchers, but it appears that environmental factors play a role. In the study area of ​​Ethiopia, houses are built with mud and the family lives with animals indoors. In industrial areas the environmental impact is less (babies are born in hospitals, disinfectants and cleaning products are used at home, etc.).

Greater diversity of the infant microbiome in Ethiopia

Another significant difference is the greater diversity of microbiomes found in Ethiopian infants, in which uncharacterized microbial species represented a larger fraction than in others. “We identified uncharacterized species belonging to the Selenomonadaceae and Prevotellaceae families, specifically present and shared only in the Ethiopian cohort”, points out the CSIC researcher. Escherichia coli and Bifidobacterium spp. they are the most shared species in the microbiomes of European children.

According to the research team, a locally produced fermented food, Ethiopian flatbread called injera (made with local cereal flour or teff) may contribute to the greater diversity seen in the gut of Ethiopian babies with bacteria originating from the environment and/or fermented foods. .

The microbial species ‘Escherichia coli’ and ‘Bifidobacterium spp’. are the most shared species in the microbiomes of European children

According to the authors, this is the first study that addresses the transfer of mother-infant microorganisms in non-Western communities. Taken together, their findings highlight the fact that diet and lifestyle can affect the composition of the gut microbiome not only through differences in diet, drug consumption, and environmental factors, but also through their effect on patterns of distribution of mother-infant strains.

“Although diet can be a determinant in the formation of the infant microbiome, our results in the mother-infant exchange of Prevotellaceae spp. they could not rule out that maternal transmission early in life could also contribute to the divergence in the composition of the microbiota associated with non-Western communities”, points out Collado.


Manara et al., “Maternal and dietary microbial sources shape the infant microbiome of a rural Ethiopian population”, current biology (2023)

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