GAINESVILLE, Fla.-- Fighting tooth decay could someday be as simple as using a mouth rinse, thanks to a University of Florida researcher who has genetically altered the bacterium known to cause tooth decay into a form that may permanently prevent the disease.

The friendlier version appears safe and long lasting, and apparently has a sweet tooth of its own, thriving on a high-sugar diet in the laboratory, reports UF dentist Jeffrey Hillman in the February issue of the journal Infection and Immunity. Hillman constructed a new strain of the decay-causing bacterium Streptococcus mutans for use in replacement therapy.

Streptococcus mutans, a naturally occurring bacterium found in the mouth, breaks down food sugars, resulting in the formation of lactic acid. Over time, the acid destroys tooth enamel, causing cavities.

"Based on this accepted theory of the decay process, we eliminated the gene responsible for lactic acid production from a strain of Streptococcus mutans," said Hillman, a professor of oral biology at UF's College of Dentistry. "The new strain does not produce lactic acid and therefore will not cause decay." Hillman studied the new strain -- called an effector strain -- in the laboratory and in rat models. He found it dominated the naturally occurring bacterium and blocked it from colonizing the tooth surface.

"The effector strain didn't cause tooth decay even when the animals were fed a high-sugar diet. In fact, sugar actually helps our strain to colonize," Hillman said. "It is genetically stable and should be safe for humans."

Hillman's new strain does not cause disease or predispose the host to other diseases. It also appears to stay permanently on teeth. Hillman said he believes the effector strain can eliminate most tooth decay.

"There is no way to know how much of the world's tooth decay is caused by Streptococcus mutans," Hillman said. "Most studies suggest that of the 500 or so bacter
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Contact: Connie Daughtry
cdaughtry@dental.ufl.edu
352-392-4431
University of Florida
7-Feb-2000