Researchers at LDS Hospital and the University of Utah may be hot on the trail of one of the world's greatest killers, atherosclerosis.

They think the common bacterium chlamydia pneumoniae, which causes a form of pneumonia, may also cause or influence development of atherosclerosis. The disorder, in which fatty deposits clog arteries, leads to coronary artery disease, strokes and other illness.Coronary artery disease is the leading cause of heart attacks, which kill an estimated 500,000 Americans every year. Strokes also take a huge toll. If the discovery is substantiated - and if it leads to a simple antibiotic treatment for atherosclerosis - the health savings would be incalculable.

However, physicians who are working on the discovery stress that while they know there is some sort of connection between the chlamydia pneumoniae and atherosclerosis, they don't know if it's a cause-and-effect connection. That will take further studies.

The research project was conducted at LDS Hospital by Dr. Joseph B. Muhlestein, the lead investigator; Dr. Elizabeth H. Hammond, John F. Carlquist, Ellen Radicke, Matthew J. Thompson, Dr. Labros A. Karagounis, Dr. Marion L. Woods and Dr. Jeffrey L. Anderson, all of whom are based at the University of Utah. Their report is published in the June 1 issue of The Journal of the American College of Cardiology.

They studied specimens of plaque deposits from 90 heart disease patients who were treated at LDS Hospital from January 1993 to July 1994. Also, they examined deposits from 12 normal people and 12 people who had coronary problems because of heart transplants.

They exposed the specimens to a dye that would attach only to the bacteria. To their surprise, they found that the chlamydia was present in 79 of the 90 samples from people with coronary artery disease.

On the other hand, they found chlamydia bacteria in only one out of the 24 other specimens, or about 4 percent.

The result shows a "significant association," said Muhlestein, who is director of research at LDS Hospital's cardiac catheterization lab and an assistant professor of medicine at the U. School of Medicine.

He added that the study is an advance on suspicions about the connection that first surfaced in Finland, and a study in Seattle. This project was able to come up with incidence figures and also check results against two control groups, unlike any other on the subject.

The findings may turn out to be similar to the recent discovery that most ulcers are caused not by stomach acid but by bacteria.

A new round of studies began Thursday, in which rabbits are injected with the bacteria and then checked to see if they develop atherosclerosis. It should take about six months to complete.

If causation really exists, the team thinks, it could be because people are exposed to the bacteria and develop pneumonia. An estimated 50 percent of people have antibodies showing they were exposed to the bacteria by the time they are 20, which rises to 77 percent by age 60.

The Journal article makes this argument: "An infectious cause for coronary artery disease has been proposed by some but is currently not accepted" by the medical establishment.

"However, the rise and fall of the incidence of coronary artery disease in the United States from the 1940s through the 1970s appears to emulate that of an infectious epidemic."