When Tooth Decay Becomes Fatal

26-11-2004: Oral streptococci, bacteria living in the human mouth, are capable of causing much more than just dental caries. Serious diseases such as cardiac valve inflammation have also been shown to be triggered by this bacterium. A new research project, supported by the Helmholtz Association of National Research Centres, is poised to take a closer look at the pathogens that cause these problems and subsequently develop control studies. Three scientific institutes are participating in the project, which is being coordinated by the German Research Centre for Biotechnology (GBF) in Braunschweig.

Several hundred kinds of bacteria live in the human oral cavity. Approximately two dozen of these belong to the genus Streptococcus, among them the species Streptococcus mutans and Streptococcus salivarius. Some of these oral streptococci are responsible for plaque build-up and tooth decay - a nuisance but hardly life threatening. However, when they manage to enter the bloodstream - as the result of an injury for example - these microorganisms can cause blood poisoning (sepsis). If the bacteria reach other parts of the body through our circulatory system they can sometimes lead to abscesses in the throat, lungs or liver and even cause life threatening cardiovalvulitis and heart disease.

There is no cause for alarm however as not every bacterial presence in the bloodstream has dramatic consequences. Oral streptococci really only have the potential to become a problem if they appear in large numbers in a weakened immune system. Nonetheless, experts are concerned that their clinical importance will increase in the foreseeable future. Professor Singh Chhatwal, a streptococcus expert and department director at the GBF, explains why this is so: "On the one hand, our lifestyle with its sugar-rich diet favours the growth of tooth decay bacteria, while paradoxically, on the other hand, our good dental care is accompanied by new risks. More dental care increases the chances for small wounds in the oral cavity through which oral streptococci can enter the bloodstream." Increasing life expectancies and the related immune deficiencies of the elderly also make it easier for otherwise harmless tooth decay bacteria to be transformed into dangerous pathogens. Blood poisoning as a result of tooth decay, for example, is being observed more frequently in children with leukaemia.

The most worrisome development, warns Prof. Chhatwal, is that streptococci have a knack for quickly becoming resistant to antibiotics, which in the past have been our best weapon against bacteria. "We have also noticed," he says, "that streptococci are capable of passing their genes for resistance to other bacteria, even ones that are more dangerous." That is why Chhatwal and his research colleagues feel it is absolutely essential to learn more about oral streptococci. Until the mechanisms that turn harmless mouth inhabitants into dangerous pathogens are better understood Prof. Chhatwal advises the best prophylaxis is to brush your teeth and lead a healthy lifestyle. He emphasises that people with poor oral hygiene and weak immune systems are the most prone to infection.