TOSS away that toothbrush. A single trip to the dentist as a toddler could be
all you need to keep tooth decay away for life. But there鈥檚 a catch. You have to
be willing to open your mouth to an invasion of genetically modified
bacteria.
The scheme involves replacing your mouth鈥檚 natural cavity-causing bacteria
with GM bacteria designed to prevent tooth decay. 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.
The GM bacteria would replace a bug called Streptococcus mutans,
which colonises most people鈥檚 mouths and causes about 85 per cent of all dental
cavities. It does this by converting sugar to lactic acid that slowly etches
away tooth enamel.
Advertisement
To make his GM bacteria, Hillman set out to find a bacterium that was
incapable of secreting lactic acid and that could kill and completely replace
the harmful S. mutans. After collecting samples from the mouths of
hundreds of patients in the early 1980s, he hit upon a strain that can wipe out
S. mutans by secreting a bacterial toxin. The toxin is deadly to other
types of bacteria too, but Hillman鈥檚 variant didn鈥檛 kill other, helpful bacteria
in the mouth or in the gut because the toxin doesn鈥檛 travel far from where it is
produced.
But the bacterium wasn鈥檛 perfect鈥攊t still secreted lactic acid and so
could cause cavities. To disarm it, Hillman and his colleagues removed the gene
that codes for lactate dehydrogenase, the enzyme that converts sugars to lactic
acid. They called the new strain BCS3-L1.
BCS3-L1 can be brushed or squirted onto the teeth in a formulation that
Hillman says tastes like chicken soup. When applied to the teeth of rats,
BCS3-L1 dramatically reduced cavities.
Hillman and his company OraGen of Alachua, Florida have not yet had
permission from the Food and Drug Administration to test the therapy in humans.
But three human subjects who volunteered to have BCS3-L1鈥檚 parent strain applied
to their teeth in the early 1980s still have no S. mutans in their
mouths. The volunteers have not passed the GM bacteria to their partners or
children, indicating that it cannot be spread by kissing.
Other researchers are working on a vaccine against cavity-causing bacteria
(快猫短视频, 15 September 2001, p 17).
But Hillman says it is much
easier to tinker with bacteria than with the human immune system.
Ideally BCS3-L1 should be swabbed onto children鈥檚 teeth at about the age of
two, before toddlers have had chance to acquire the S. mutans bug by
sharing such things as drinks with others. Hillman estimates the treatment could
cost about $100 per child and take five minutes.