Chlamydia pneumoniae, but not Bartonella quintana, is associated with coronary heart disease: results of a French case-control study.

Serologic cross-reactivity has been demonstrated between Bartonella quintana and Chlamydia pneumoniae. Therefore, the association between antibodies to C. pneumoniae and coronary heart disease (CHD) as described in the literature may be due to antibodies cross-reacting with B. quintana. To investigate this hypothesis, we evaluated, in a case-control study, the prevalence of C. pneumoniae and B. quintana antibodies among 296 cases with angiographically significant artery lesions and 170 controls without angiographically demonstrable coronary artery disease. The prevalence of C. pneumoniae antibodies was higher among cases than among controls: 69% versus 49% (P < 0.001; OR 1.39; 95% CI (1.55; 3.52)). Multiple logistic regression demonstrated that C. pneumoniae seropositivity is an independent risk factor for CHD (adjusted OR 2.31; 95% CI (1.49; 3.60)). No statistically significant association was demonstrated between B. quintana seropositivity and CHD. Antibodies to both C. pneumoniae and B. quintana were found in nine subjects (seven cases and two controls), suggesting co-infection rather than cross-reactivity.