Chlamydia pneumoniae in different coronary artery segments in the young

Chlamydia pneumoniae has emerged as the most likely pathogen to have a causative role in the development and/or for progression of atherosclerosis. Evidence for this is based on epidemiological and pathological studies. In an effort to better understand the significance of finding C. pneumoniae in atheromata, we examined coronary artery segments of young adults (15-34 years) with and without atherosclerosis. Left anterior descending coronary arteries (LAD) of 74 young adults who died suddenly were examined histologically and for the presence of C. pneumoniae by immunohistochemistry. C. pneumoniae was identified in advanced lesions (Stary types III to VI) in 17 of 32 cases (53%), and in early lesions (Stary type I-II) in 8 of 37 cases (21%), mainly at the proximal segments of the LAD. C. pneumoniae was not found in the intimal and medial layer of normal-appearing coronary arteries. C. pneumoniae was detected in the adventitia in 51 (67%) coronary arteries: in 27 of normal arteries and early lesions (64%), and in 24 of atherosclerotic lesions (75%). C. pneumoniae was found most often in macrophages, less offen in smooth muscle cells. We also observed a correlation between C. pneumoniae positivity and cigarette smoking. In conclusion: C. pneumoniae may relate to the severity of atherosclerosis in young people, and it may thus initiate atherosclerotic injury or facilitate its progression with other risk factors.