Involvement of Chlamydia pneumoniae in atherosclerosis: more evidence for lack of evidence.

During the past 15 years, many studies have been devoted to the relationship of Chlamydia pneumoniae and atherosclerosis: the serologic link has been investigated, and chlamydial organisms have been detected in lesions by electron microscopy, immunohistochemistry, in vitro cultivation, PCR, or in situ hybridization; efforts have been made to produce atherosclerosis experimentally in animals by inoculation of C. pneumoniae and therapeutic trials in humans have been undertaken. Some studies conclude that C. pneumoniae is present in cases of atherosclerosis, while others deny this, splitting the medical community into believers and disbelievers. The question, being a scientific one, should be resolved on a rational basis. After Boman and Hammerschlag reviewed the problem in 2002 (Clin. Microbiol. Rev. 15:1-20, 2002), a number of new studies were published on the subject. In this review, we critically evaluate the available data for the evidence or lack of evidence of a causal relationship for C. pneumoniae in atherosclerosis based on diagnostic and therapeutic studies performed with humans between 1992 and 2003, thereby searching mainly for concordance of evidence arising from different approaches used by different groups, at different times, and under different circumstances.