Summary

 Background: Previous work has suggested an association between Chlamydia pneumoniae infection and coronary artery disease. The infection was demonstrated by titers of antibodies - enzyme-linked immunosorbent assay or immunofluorescence, and polymerase chain reaction - and by the findings of C. pneumoniae in the atherosclerotic plaque.

Objectives: To evaluate the association between chronic infection with C. pneumoniae, as measured by a high titer of IgG antibody, and CAD. Our study was designed to explore the relationship between seropositivity to C. pneumoniae and serious coronary events, and to assess whether or not there may be an additional association between established cardiovascular factors and infection with this organism.

Methods: The serum of 130 patients with proven CAD was tested for the presence of IgG antibodies to C. pneumoniae using an ELISA test. A titer ≤1:64 using the microinfluorescence method, the recognized "gold standard," correlates with a positive result when using the ELISA method. The mean age was 57 (40-65 years). The patients, 82% male and 18% female, had either myocardial infarction (n=109) or unstable angina (n=21) 6 months before the investigation (range 3-24 months). The serum for the control group was obtained from 98 blood donors from the same area matched for age 52 (40-58 years) and sex. The donors had no known cardiac history.

Results: In the CAD group 75% of patients were positive for C. pneumoniae compared to 33% in the control group (P=0.001). No increased correlation could be demonstrated between traditional risk factors and C. pneumoniae infection, except in those patients with diabetes mellitus. We found a lower prevalence of IgG antibody to C. pneumoniae in the diabetes subgroup than in other subgroups (P<0.006), but a higher prevalence than in the control group.

Conclusions: We demonstrated a more than twofold increase in seropositivity to C. pneumoniae among patients suffering serious coronary events, and this trend was independent of gender, age or ethnic group. These findings suggest that chronic C. pneumoniae infection may be a significant risk factor for the development of CAD, but this correlation should be investigated further.
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CAD= coronary artery disease