Background. Possible relationship between Chlamydia pneumoniae (CPN) infection and atherosclerosis has been documented in many seroepidemiological, histological and biological studies. The objectives of the present study were to find out whether serological signs of active CPN infection in patients with coronary heart disease (CHD) are associated with the presence of bacterial DNA in peripheral blood and to correlate with clinical symptoms and to study the dynamics of the markers of CPN infection within a six-month follow-up. Methods and Results. Seventy-one patients with acute CHD were enrolled in the study. They underwent clinical and biochemical tests and were screened for the presence of genus- and type-specific IgG, IgA and IgM antibodies against CPN at admission and then in 3- and 6-month intervals. CPN DNA was detected in peripheral blood using nested PCR. Serological markers of active CPN infection were found in 36 patients (51.4 %) while bacterial DNA was detected in two patients only. Laboratory signs of active CPN infection did not correlate with either clinical symptoms or levels of biochemical markers. In most of the patients, titers of anti-CPN antibodies were stable throughout the follow-up. Increase in antibody titers was observed in 23 % of patients and was associated with more frequent signs of unstable angina pectoris (p=0,06) but not with higher risk of myocardial infarction within 6 months after the acute episode of CHD. Conclusions. In patients with CHD, serological markers of active infection persist for a long time. Nevertheless, their association with the course of CHD or relapse risk was not proved. Bacterial DNA was rarely detected in peripheral blood of the patients. None of the currently available laboratory tests proved adequately effective for detection of ongoing or chronic CPN infection. This project was sponsored by grant IGA MZ ČR NI/6811-3 and research plan of Natl. Inst.Publ.Health

        Key words: Chlamydia pneumoniae, antibodies, PCR, coronary heart disease, atherosclerosis.