People who live in the same home share many of the same bacteria in their mouths and guts, according to a new study published in Cell Press Blue.
"Who we decide to share our homes with can have a huge influence on our microbiomes, which has potential consequences for our health," commented first author Vitor Heidrich, a computational biologist at the University of Trento, Italy.
Researchers at the University of Trento studied the mouth and gut microbiomes of more than 400 people living in 207 households. They analyzed saliva and stool samples, allowing them to study bacteria in both the mouth and gut at the same time.
Instead of looking only at different types of bacteria, the scientists focused on specific strains. If two people had the same strain, it strongly suggested that the bacteria had been passed between them. Using advanced genetic analysis, the team was able to identify whether people carried identical bacterial strains.
They found that people living together shared more bacterial strains with each other than with other people in the same community. This was likely more seen among couples who lived together, as they shared close physical contact, including kissing, which makes it easier for mouth bacteria to spread between partners. Couples shared about 44.4% of their oral bacteria on average, compared with 19.5% of their gut bacteria.
Among 66 healthy adults monitored for around three and a half months, about 14.7% of oral bacterial strains were replaced, compared with just 5.8% of gut strains. This suggests that the mouth is a more open environment where bacteria can move in and out more easily.
Although many of the bacteria living in our bodies are harmless or helpful, some of the bacteria that spread between people may be linked to health problems. The researchers found that some of the most easily shared gut bacteria were associated with Type 2 Diabetes and poor heart health. Some of the most transmissible mouth bacteria were linked to colorectal Cancer and infections that can become a problem when the immune system is weakened.
"Understanding natural microbiome transmission can inform more targeted artificial transmission solutions," said Heidrich. "If we can identify the characteristics that make some microbes more transmissible than others, and the constraints that make beneficial microbes less transmissible, we can apply that to make fecal microbiota transplants much more effective."
The findings suggest that people living together can influence each other's microbiomes in ways that may affect health, although more research is needed to understand the long-term impact.
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