The mouth is the second most diverse microbial system in the human body after the gut—but researchers at Penn Dental Medicine say it behaves very differently when it comes to long-term health.
In a study published July 16 in Microbiome, researchers compared the oral microbiomes of Nigerian children living with HIV, those exposed to the virus but uninfected, and those unexposed. Their findings suggest that, unlike in the gut—where stability of the microbial community is considered a marker of good health—a dynamic, adaptable oral microbiome may be more beneficial.
“Oral microbiome shows less community change over time in children living with or exposed to HIV, which we hypothesize may be linked to a reduced capacity to adapt to environmental changes,” the researchers wrote.
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565 children with tooth decay
The team studied 565 children with varying degrees of tooth decay. They collected 1,960 supragingival plaque samples and used a metataxonomic approach to sequence a 478 base-pair region of the bacterial rpoC gene, a common marker used to identify bacterial species. This helped determine which microbes were present and how they related to disease risk.
They also mapped how the microbial communities varied from the front to the back of the mouth and analysed bacterial stability at three time points. The children who were either infected with or exposed to HIV showed more homogeneous microbial communities across the mouth, in contrast to the distinct bacterial profiles typically found between the front and back teeth in healthy children.
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Oral microbiome more active in unexposed kids
Children unexposed to HIV had higher microbial turnover—meaning the composition of oral bacteria changed more over time. According to lead researcher Dr. Modupe O. Coker, this is a sign of a more adaptable and possibly healthier oral environment.
Coker added that lower microbial turnover was associated with increased frequencies of cavity-causing bacteria, potentially raising the risk of tooth decay in children affected by HIV.
“As a translational scientist, I hope we can keep looking at novel ways to use this information to understand disease and to prevent or treat it,” she said.