The researchers were looking for two things when they swabbed subjects' gums. First, they wanted to see which bacteria were present by analyzing DNA signatures found in dental plaque. They also monitored whether the subjects' bodies were treating the bacteria as a threat. If so, the swab would show higher levels of cytokines, compounds the body produces to fight infection.
The results of the study were published in the journal Infection and Immunity.
"When you compare a smoker and nonsmoker, there's a distinct difference," said Kumar. "The first thing you notice is that the basic 'lawn,' which would normally contain thriving populations made of a just few types of helpful bacteria, is absent in smokers."
The team found that for nonsmokers, bacterial communities regain a similar balance of species to the communities that were scraped away during cleaning. Disease-associated bacteria are largely absent, and low levels of cytokines show that the body is not treating the helpful biofilms as a threat.
"By contrast," said Kumar, "smokers start getting colonized by pathogensbacteria that we know are harmfulwithin 24 hours. It takes longer for smokers to form a stable microbial community, and when they do, it's a pathogen-rich community."
Smokers also have higher levels of cytokines, indicating that the body is mounting defenses against infection. Clinically, this immune response takes the form of red, swollen gumscalled gingivitisthat can lead to the irreversible bone loss of periodontitis.
In smokers, however, the body is not just trying to fight off harmful bacteria. The types of cytokines in smokers' gum swabs showed the researchers that smokers' bodies were treating even healthy bacteria as threatening.
Although they do not yet understand the mechanisms behind these results, Kumar and her team suspect that smoking is confusing the normal communication that goes on betw
|Contact: Purnima Kumar|
Ohio State University