The community of people living around you could influence the community of microbes living inside you.

The largest and most diverse review to date found evidence that the people you live with and were raised with may have a greater impact on your microbiome than certain lifestyle factors, age or even genetics.

If the results are correct, then the billions of microbes that inhabit our bodies could be more contagious than we thought. And that could have serious consequences for public health.

Research by microbiologist Nicola Segata of the University of Trento in Italy fails to show how microbes jump directly from individual to individual, instead illustrating how much our gut and mouth bacteria are shared with those who surrounding us.

Social interactions, the authors conclude, could help shape an individual’s community of microbes, and this, in turn, could “play a role in microbiome-associated diseases.”

The results are based on more than 9,000 stool and saliva samples taken from participants with known links to each other. These communities were deliberately sampled in 20 different countries around the world, not just in western or developing countries.

The results strongly suggest that the trillions of symbiotic cells in our body can spread efficiently between human hosts, even following brief encounters in public.

The strains of bacteria shared between study participants were found to be “extensive”. In fact, researchers have identified more than 10 million cases of bacterial strains shared between mothers and infants, members of the same household, or community members.

Previous studies have shown that a mother helps jump-start her child’s microbiome in the first few months of life by sharing some of her own microflora with him, usually through vaginal birth, breastfeeding, exchanging saliva or touch.

It is also known that a person’s microbiome can fluctuate throughout their lifetime depending on what they eat, how much they exercise, or the environment they live in.

In comparison, human-to-human transmission has not been as widely studied. The results of the current review suggest this is an oversight.

As expected, mother-to-child transmission was the most important route of exposure. In 711 cases, about 50% of the same bacterial strains were shared between mother and child during the first year of life, and 16% of these strains came specifically from the mother.

Moreover, this seeded community of microorganisms could still be detected late in adulthood, although at lower percentages. By age 30, for example, the average person in the study had retained about 14% of their mother’s original bacterial strains. Even at age 85, a mother’s most transmissible strains were still present in her offspring.

As a person ages, the microbial influence of the mother is counterbalanced by other relationships. Who a person lives with and interacts with on a daily basis seems to have an increasingly important impact on the composition of their microbiome.

After the age of four, for example, researchers have found that a child shares equal percentages of bacterial strains from both mother and father. Additionally, the longer identical twins lived apart, the fewer microbial strains they shared in their gut.

In total, about 12-32% of bacterial strains in the gut and mouth are shared with others under the same roof. Similar lifestyle factors were not sufficient to explain the results.

“As adults, the sources of our microbiomes are primarily the people we come into close contact with,” Segata says.

“The duration of interactions – think for example of students or partners sharing an apartment – is roughly proportional to the number of bacteria exchanged.”

When the authors looked to larger communities, they noticed a similar but smaller relationship.

Less than one percent of bacterial strains appeared to pass from household to household in the same rural community, making it a relatively rare form of transmission. That said, bacterial species transmissibility with rural communities was very consistent across all datasets.

In about 67% of the communities studied, individuals from the same village but from different households shared more bacterial strains than with households from other villages.

The results suggest that even superficial interactions can influence a person’s microbiome, for better or for worse. While some microbes can have health benefits, others can weaken the microbiome, leaving individuals vulnerable to disease.

“The transmission of the microbiome has important implications for our health, since some non-communicable diseases (such as cardiovascular disease, diabetes or cancer) are partly linked to an altered composition of the microbiome”, explains Segata.

“The demonstration that the human microbiome is transmissible might suggest that some of these diseases (currently considered non-communicable) could, at least to some extent, be transmissible.”

The study was published in Nature.

Source link

Leave A Reply