C-reactive protein levels and viable Chlamydia pneumoniae in carotid artery atherosclerosis

Background and Purpose-An elevated serum level of C-reactive protein, an in flammatory marker, is an independent predictor of stroke and coronary arter y disease. To determine whether chronic infection with Chlamydia pneumoniae , which has been identified in atherosclerotic plaques. is responsible for systemic inflammation, we studied the association between serum C-reactive protein levels and infection of carotid artery atherosclerotic plaque with viable C pneumoniae. Methods-Serum C-reactive protein levels were obtained before endarterectomy for carotid artery stenosis. Plaques were tested for C pneumoniae mRNA, an indicator of viability, and DNA by polymerase chain reaction of DNA and cD NA, respectively. Results-Forty-eight samples were studied, of which 18 (38%; 95% CI, 23 to 5 0) were infected with viable C pneumoniae as evidenced by isolated chlamydi al mRNA. All IS of these samples, plus 1 additional sample, were positive f or chlamydial DNA. Serum C-reactive protein levels were higher in those wit h viable C pneumoniae compared with those without infection (median, 8 mg/L versus undetectable P = 0.045 by Wilcoxon rank-sum test). In multivariable models, C the only independent predictor of the presence of viable C pneum oniae was a detectable C-reactive protein level (odds ratio. 4.2; 95% CI, 1 .1 to 17; P = 0.04). Conclusions-Viable C pneumoniae are present in a substantial portion of car otid artery atherosclerotic plaques and are associated with increased serum C-reactive protein levels. These findings may explain the link between ele vated C-reactive protein levels and the risk of cardiovascular disease and stroke but should be reproduced in a larger cohort.