Influence of industrialization on the microbes that babies share with their mothers

2023-05-09 13:15:05

The origin of the human microbiome begins at birth, when the first microorganisms that inhabit our body are mainly acquired from the mother. Until now, it has been studied how the type of delivery (natural or caesarean section), antibiotic prophylaxis and feeding method, 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, had not yet been analysed.

Now, an international research team co-directed by Nicola Segata (University of Trento in Italy), Edoardo Pasolli (University of Naples in Italy) and María Carmen Collado (Institute of Agrochemistry and Food Technology (IATA), of the Higher Council for Scientific Research (CSIC) in Spain), has explored the mother-infant microbiome exchange through the metagenomic analysis of more than 700 samples from newborns (less than one year of age), children up to 12 years of age and their mothers, obtained in Ethiopia, and comparing them with others from countries such as Ghana and Tanzania, as well as other more industrialized countries such as Italy and Sweden.

The study results show that the composition of the microbiomes of Western and non-Western newborns overlapped during the first months of life more than later, reflecting similar initial breast milk-based diets. However, “Ethiopian and other non-Western babies shared a smaller fraction of the microbiome with their mothers than most Westernized populations,” Collado reveals. 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.

The reason for this difference is not clear to the researchers, but it appears that environmental factors play a role. “In the study area of ​​Ethiopia, the houses are built with mud and the family lives with animals inside the house. In industrial areas there is less environmental impact (babies are born in hospitals, sanitizers are used at home, etc.)”, argues the researcher.

Source of drinking water by CSIC researchers in Ethiopia. (Photo: César Hernández / CSIC)

Increased diversity of the child microbiome in Ethiopia

Another significant difference found in the research is the greater diversity of microbiomes found in Ethiopian babies, with uncharacterized microbial species representing a larger fraction than the rest. “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. The samples from Ethiopia come from the collaboration with Mari Olcina (University of Valencia), MOSSolidaria ONGD and the GeNaPi project team, which includes staff from the CSIC and the University of Valencia.

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

This is the first study to address the exchange of mother-infant microorganisms in non-Western communities, according to the researchers. Taken together, their findings highlight the fact that habitual diet and lifestyle can affect the composition of the gut microbiome not only through differences in diet, medication consumption, and environmental factors, but also through through its effect on the distribution patterns of mother-infant strains.

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

The study is titled “Maternal and food microbial sources shape the infant microbiome of a rural Ethiopian population”. And it has been published in the academic journal Current Biology. (Source: CSIC)