NEW YORK, (Reuters Health) – The increased risk of cardiovascular disease and stroke associated with elevated C-reactive protein levels may be explained by the finding of viable Chlamydia pneumoniae in many carotid artery atherosclerotic plaques, researchers report it the December issue of Stroke: Journal of the American Heart Association.
"Half the plaques we studied had evidence of viable C. pneumoniae and in those that had viable C. pneumoniae, C-reactive protein levels tended to be higher," Dr. S. Claiborne Johnston from the University of California, San Francisco, told Reuters Health. "That suggests a link between C-reactive protein and atherosclerotic disease."
Dr. Johnston and colleagues studied C-reactive protein levels and samples of carotid artery atherosclerotic plaques taken from 46 patients who underwent endarterectomy for carotid artery stenosis.
Of the 48 carotid artery atherosclerotic plaque samples taken, viable C. pneumoniae infection was found in 18. These samples and one other were positive for chlamydial DNA, Dr. Johnston's team found.
Compared with samples not infected with viable C. pneumoniae, patients with viable C. pneumoniae had higher concentrations of C-reactive protein (p = 0.045). Patients with detectable levels of C-reactive protein were twice as likely to have viable C. pneumoniae compared with patients without detectable levels of C-reactive protein (p = 0.06).
Multivariate analysis showed that detectable levels of C-reactive protein was the only independent predictor of viable C. pneumoniae (odds ratio 4.2, p = 0.04), the investigators report.
"This study provides evidence that Chlamydia matters," Dr. Johnston said. "It may explain why elevated markers of inflammation are associated with the risk of stroke and heart disease."
Before C. pneumoniae can be viewed as a treatable cause of atherosclerotic disease progression, Dr. Johnston said, one needs to know if C. pneumoniae is a cause of cardiovascular disease and whether it can be treated. "However, these are two things we do not know yet."