Summer 2002      

Finding clues to caries and more in DNA









Window of Infectivity


Page W. Caufield, D.D.S., Ph.D., is Professor and Head of the Division of Diagnostics, Infectious Disease and Health Promotion

Dr. Page W. Caufield, a distinguished microbiologist/infectious disease specialist, was the first to demonstrate that mutans streptococci—one form of bacteria responsible for dental caries—are transmitted from mother to infant during a discrete interval, which has been designated a “window of infectivity” occurring when the infant is around 26 months of age. Because mother and infant enjoy intimate contact and have similar immune systems, unlike those of fathers, infants acquire members of the indigenous oral bacteria from mothers, not fathers.

Dr. Caufield’s premise is that by genetically identifying at-risk children early in life, it will be possible to treat them more easily and effectively. “What we now know,” he says, “is that we are on our way to developing an anti-caries antibiotic.” He predicts that it will not be long before dentists will be able to treat at-risk infants with this antibiotic and then seal all the spaces in the young child’s mouth where bacteria could live.

To track the transmission of oral bacteria from mother to child, Dr. Caufield and his team use DNA fingerprinting techniques. In a study recently funded by the NIH, Dr. Caufield will use these and other molecular tools to discover why some children are more susceptible to a severe form of tooth decay called rampant caries. Using bacterial profiling, the investigative team hopes to reveal what genetic factors in the bacteria are associated with this severe form of dental caries. These same tools can be applied to uncovering the genetic basis for other infectious diseases, including ulcerative colitis and peptic ulcers.

In a similar fashion involving genetic codes, Dr. Caufield is also looking at the genetic diversity of different strains of Streptococcus mutans collected from around the world. “By comparing DNA sequences, we can construct a family tree, so to speak, of the bacteria from ethnically diverse humans. Since bacteria and their human hosts evolved together over time, the human tree and the bacterial tree should be similar—at least, that is what we expect to find.”

Dr. Caufield and his colleagues have sampled people in remote areas, including the rain forest of Central Africa and in China, Brazil, New Zealand, Japan, and the U.S. Dr. Caufield will be part of a team of anthropologists, dentists, and physicians who will soon visit the Wapasha tribe deep within the Amazon of South America.

As a result of sampling bacteria from all over the world, the team has discovered several peptide antibiotics made by oral bacteria that are active against many of the now antibiotic-resistant bacteria common to other areas of the body. Several of these antibiotics received U.S. patents and are now being made in fermenters for large-scale production. One of the mutacin antibiotics is also active against the bacillus associated with anthrax, and therefore is a potential weapon against bioterrorism.