Specificity of detection of Chlamydia pneumoniae in cardiovascular atheroma: evaluation of the innocent bystander hypothesis

Chlamydia pneumoniae has been detected in atherosclerotic plaque, raising the question of whether this detection is specific to atheromatous tissue. To evaluate this question, we tested cardiovascular and non-cardiovascular tissue samples from 38 autopsy cases by polymerase chain reaction and immunocytochemistry. We also tested 33 granuloma biopsy specimens, as the organism has been detected in macrophages. C. pneumoniae was detected in coronary artery tissue from 13 (34%), lung from 5 (13%), liver from 4 (10%), and spleen from 2 (5%) of the 38 autopsy cases (P < 0.05 for comparison of proportion of positive coronary arteries with that of each of the other types of tissue). Of the 21 cases with at least one positive tissue sample, 11 had only a positive cardiovascular tissue (coronary artery, venous bypass graft, or myocardium), 7 had both cardiovascular and non-cardiovascular positive tissues, and 3 had only a non-cardiovascular positive tissue. C. pneumoniae was thus detected relatively infrequently in non-cardiovascular tissues, and its detection in these tissues was usually in association with its detection in cardiovascular tissue from the same patient. The organism was also infrequently detected in granulomatous tissue (3/33 specimens). These findings demonstrate that C. pneumoniae is more frequently found in atherosclerotic than normal tissue and support the hypothesis that C. pneumoniae has a role in the pathogenesis of atherosclerosis.