Chlamydia pneumoniae Seropositivity and Hyperhomocysteinemia Are Linked in Patients with Atherosclerosis

Atherosclerosis, with its different clinical manifestations, is the major cause of morbidity and mortality in the developed countries. Chlamydia pneumoniae infection and the ensuing chronic inflammation have been claimed to contribute to the atherosclerotic process (1). Concurrently, epidemiologic evidence suggests that hyperhomocysteinemia is associated with an increased atherosclerotic risk (2). Both C. pneumoniae infection and hyperhomocysteinemia have been assumed to increase the atherosclerotic risk independently of each other and independently of the classic risk factors.In vitro, the growth of C. pneumoniae is enhanced in serum-free media and particularly by the depletion of lysine or methionine (3). In human metabolism, homocysteine is produced by demethylation of methionine, and defects in the recycling pathway (in which homocysteine is remethylated to methionine) are one cause of hyperhomocysteinemia (4). This constellation prompted us to investigate whether C. pneumoniae seropositivity and plasma homocysteine concentrations are related in patients with established atherosclerosis.Approval for this project was obtained from the ethics committee of the University Hospital of Zurich. All patients gave informed consent to participate. The study subjects consulted our ward for follow-up visits and were recruited consecutively. Inclusion criteria were that subjects had to be male and have had an established atherosclerosis defined as the following: ( a ) history of myocardial infarction or …