A mouthful of genetically modified bacteria could keep tooth decay away for life. The scheme involves replacing your mouth鈥檚 natural cavity-causing bacteria with GM bacteria specially designed to prevent tooth decay.
The GM bacteria would be swabbed onto to children鈥檚 teeth at about age two, before they acquire the natural strain. The treatment could take just five minutes cost about $100.
鈥淢y goal was to construct a good version of bad bacteria,鈥� says dental researcher Jeffrey Hillman at the University of Florida in Gainesville.
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The bad bug is called Streptococcus mutans and currently colonizes almost everyone鈥檚 mouth. It causes about 85 per cent of all dental cavities by converting sugar to lactic acid, which slowly etches away the enamel on teeth.
Toxic killer
Hillman set out to find a sister strain to S. mutans that was incapable of secreting lactic acid and that also could kill and completely replace S. mutans. After collecting samples from the mouths of hundreds of patients in the early 1980s, he hit upon a strain that could annihilate S. mutans by secreting a toxin known as mutacin 1140. However, the strain still secreted lactic acid, so it still caused dental cavities.
To disarm the new strain of its ability to cause tooth decay, Hillman removed the gene that codes for lactase dehydrogenase, the enzyme that converts sugars to lactic acid. It took several years, but in the mid-1990s, he and his colleagues finally came up with a non-cavity causing strain they call BCS3-L1.
BCS3-L1 can be brushed or squirted onto the teeth in a formulation that Hillman says tastes like chicken soup. It dramatically reduced cavities in rats but Hillman, and his company OraGen Inc, have not yet received permission from the US Food and Drug Administration to test the therapy in humans.
However, three human subjects who volunteered to have BCS3-L1鈥檚 parent strain applied to their teeth in the early 1980鈥檚 still harbour only it and no S. mutans. The volunteers have not passed the strain to their wives and children, evidence that it cannot be spread by kissing.
Other researchers are working on a vaccine against cavity-causing bacteria. But Hillman believes it is much easier to tinker with bacteria than with the human immune system.
The new research was presented at the American Association for the Advancement of Science鈥檚 2002 annual meeting in Boston.