UF Dental Researcher Develops Genetically Altered Bacteria Strain That May Fight Cavities For A Lifetime

The friendlier version appears safe and longlasting, 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 bacterial species in the mouth, Streptococcus mutans causes the majority of decay."

Hillman added that clinical trials would help determine if one application is all that is needed for lifetime protection. The proposed studies will involve squirting a liquid solution of the effector strain on the patients' teeth. He said he hopes to start adult clinical trials this year.

"The ideal application would be to treat infants when their first teeth appear. Infants normally acquire Streptococcus mutans via contaminated saliva from their mother or primary caregiver," Hillman said. "The child would simply visit their dentist for a squirt of solution on their teeth. The approach also is designed for use in older children and adults."

Hillman's effector strain shows promise, said Dennis Mangan, chief of the Infectious Diseases and Immunity Branch at the National Institutes of Health's National Institute of Dental and Craniofacial Research.

"Years of hard work by Dr. Hillman and other oral researchers are coming to fruition. The mechanisms by which bacteria adhere to and grow on the teeth as biofilm communities, and then convert sugar to acids that damage the enamel, after enamel are extremely complicated," Mangan said. "Dr. Hillman's work exploits this knowledge in a clever, yet scientifically feasible manner and takes us one step closer to the day when everyone will be free from dental caries throughout their lifetime."

Don't toss those toothbrushes. Even if Hillman's new strain is successful, it will never replace a good toothbrushing.

"Good dental hygiene will always be necessary because of plaque buildup," Hillman said.

A National Health Spending Trends report indicates that $48 billion was spent on dental services in 1996. Hillman says the future treatment would result in dramatic savings for patients.

For the past 20 years, the National Institute of Dental and Craniofacial Research has funded Hillman's research, which has resulted in a number of product patenting and licensing agreements. OraGen, a biotechnology company located in Alachua, Fla., is licensing the new UF technology.