Children acquire cariogenic bacteria from inside and outside the family

BOSTON, USA: Previous studies have shown that children acquire cariogenic pathogens, like Streptococcus mutans, mainly from their mothers through interpersonal contact, such as the sharing of cutlery or kissing each other on the lips. However, new research has now suggested that intra- and extra-familial sources other than maternal also play a part in the transmission of S. mutans, the primary bacterium associated with dental caries.

S. mutans is considered to be transferred between humans. Children typically have more than one strain of the pathogen and share at least one of these strains with their mother or a family member. However, 72 percent of children in the current study had one or more S. mutans strains that were not found in participating household members. Therefore, the researchers suggested that these strains came from outside the home, possibly from other children in the population.

“While the prevailing theory on S. mutans transmission suggests mother-to-child transmission as the primary route of infection, in this study 40 percent of children shared no strains with their mothers,” said study author Stephanie Momeni, a doctoral candidate in the Department of Biology at the University of Alabama at Birmingham in the U.S. Interestingly, 22.8 percent of the children shared 37 strains only with another child in the household (siblings or cousins), demonstrating another dimension of inter-familial transmission.

In total, the researchers evaluated 13,145 S. mutans isolates from 119 African-American children and from at least one family member living in the same household, since not all family members chose to participate in the study in each case. More than one family member was evaluated for 76 percent of the children, with an average of 3.24 family members per child, including extended family. Aside from participating family members, the study evaluated S. mutans isolates of interacting children.

“While the data supports that S. mutans is often acquired through mother-to-child interactions, the current study illuminates the importance of child-to-child acquisition of S. mutans strains and the need to consider these routes of transmission in dental caries risk assessments, prevention and treatment strategies,” Momeni stated.

According to the researchers, further analysis with an alternate bacterial typing method is needed to confirm these findings. They presented the results of their study, titled “Evidence for horizontal transmission of streptococcus mutans among children and their family members by Rep-Pcr,” at the American Society for Microbiology Microbe meeting in Boston on June 17.