Common phenomenon
Gum disease, cardio disease link shared in developed nations career in field

By LOIS BAKER
Contributing Editor

A study of a group of Germans conducted by researchers in the School of Dental Medicine suggests that the relationship between gum disease and cardiovascular disease may be a common phenomenon in developed countries.

The study, presented today at the International Association of Dental Research (IADR) meeting in San Diego, found periodontal disease bacteria in samples of fatty plaque removed from the carotid arteries of 106 German subjects undergoing a procedure to unclog the large arteries in the neck.

The bacteria were the same types as those found in carotid plaque from an earlier study of U.S. residents.

In a related study using a subset of samples from the German cohort, rather than looking for evidence of particular oral bacteria using specific probes, researchers cast a broad net, gathering many pieces of DNA and matched their gene sequences with known pathogens.

They identified a number of different bacteria in the carotid samples, a finding that supports the "infectious burden" hypothesis proposed by scientists, which postulates a relationship between the number of infections an individual experiences and the risk for developing atherosclerotic plaques.

UB dental researchers have been at the forefront of research showing a link between the bacterial inflammation of periodontal disease and coronary disease. They currently are involved in a $7.3 million effort funded by the National Institute of Dental and Craniofacial Research to plan and conduct a pilot study for a clinical trial of the impact of periodontal disease treatment on prevention of second heart attacks.

Samples of plaque for both studies were obtained from patients with chronic periodontal disease who were undergoing endarterectomy, the process of cleaning away fatty plaque from the walls of the carotid arteries, the large vessels on either side of in the neck.

The initial study targeted specific bacteria—Chlamydia pneumoniae, human cytomegalovirus, and Herpes simplex—in 138 samples from 106 German subjects (29 women and 77 men) between the ages 43-89. Analysis showed that 75 percent of the samples contained one or more of the targeted bacteria and that 56 percent were positive for specific oral bacteria.

Nearly all of the plaque samples showed moderate to high levels of C-reactive protein, a marker for inflammatory activity associated with bacterial infection and the development of atherosclerosis.

"We weren't surprised to find periodontal bacteria in the carotid arteries of this German cohort, but we expected some variation from those found in our U.S. cohorts," said Violet Haraszthy, assistant professor in the School of Dental Medicine and lead author on the study. "This is an entirely different population with a different genetic profile.

"But we found the same bacteria, which supports our earlier studies indicating that oral infection plays a role in atherogenesis."

The study of pathogenic burden involved samples from seven participants in the larger group.

"We wanted to find out what else was there, and we found evidence for the presence of a number of different bacteria," said Joseph Zambon, professor of periodontics in the dental school and senior author of this study.

"Did these bacteria cause the plaque to develop, or did the bacteria just get trapped in the fatty deposits already forming? We don't know that yet," he said. "But the finding does support the idea that there may be many organisms involved in atheromas. And our data suggests that certain kinds of oral bacteria are more important than others," Zambon noted.

Additional researchers on the studies were Margaret Zambon and Shawn Jordan, graduate students and research aides in the UB School of Dental Medicine; Gregor Zafiropoulos from Berlin Free University, and Nick Mastragelopulos of City Hospital, Heinsberg, Germany.