Sharing of a bacterium related to tooth decay among children and their families
Date:June 20, 2016
Source:American Society for Microbiology
Research presented at the ASM Microbe research meeting
provides compelling evidence that children acquireStreptococcus mutans, the
bacterium most frequently associated with dental caries, from intra- and
extra-familial sources besides their mother.
Children typically have more than one strain (i.e.,
genotype) of S. mutans and most share at least one strain with mother or a family
member. However, 72% of children in this study had 1 or more S. mutans strains
not found in participating household family members indicating these strains
likely came from outside the home (extra-familial transmission), possibly from
other children in the population.
S. mutans colony morphology "While the prevailing
theory on S. mutanstransmission 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 Stephanie Momeni, a doctoral candidate
in the Department of Biology at the University of Alabama at Birmingham.
Interestingly, 27 children (22.8 percent) shared 37 strains only with another
child in the household (siblings or cousins), demonstrating another dimension
to inter-familial transmission.
"Of the children that did not share strains with any
household members, 33 percent (53/157) were found to have only 1 isolate,
indicating these strains to be rare or transient," said Momeni. This is
important since it suggests that approximately one-third of strains analyzed
may not be clinically relevant and can confound the search for strains related
to the disease. It also suggests these strains are highly transmissible but may
not become established strains due to bacterial competition or host immune
factors. [image: S. mutans colony morphology].
S. mutans is the primary bacterium most frequently
associated with dental caries and is considered to be transferred from other
humans. In total, S. mutans isolates (N=13,145) from 119 African American
children having at least 1 household family member were evaluated. More than
one family member was evaluated for 76% of children (mean=3.24, range 1-11).
The strength of this study is that it evaluates interacting children as well as
all participating residential household family members (including extended
family). Strain types were determined using a bacterial typing method known as
repetitive extragenic palindromic PCR (rep-PCR). For each rep-PCR genotype,
children were evaluated as either sharing or not sharing the strain with any
household members. Since children in this study had between 1-9 genotypes, a
total of 315 genotype cases were evaluated.
"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," said Momeni.
Further analysis with an alternate bacterial typing method
is needed to confirm these findings and it is important to note that not all
household family members chose to participate in the study.
Momeni will present her research, conducted in the
laboratory of Noel Childers, DDS, Joseph F. Volker Endowed Chair and Chair of
UAB's Department of Pediatric Dentistry, at the American Society for
Microbiology MICROBE Meeting in Boston, MA on June 17. The National Institute
of Dental and Craniofacial Research provided research funding for the project.
The above post is reprinted from materials provided by
American Society for Microbiology. Note: Materials may be edited for content