Atherosclerosis in dialysis patients: does Chlamydia pneumoniae infection contribute to cardiovascular damage?

Cardiovascular risk in the dialysis population is exceedingly high, and there is now convincing evidence that inflammation is strongly linked to atherosclerosis in this population. The source of inflammation in dialysis patients still remains undefined. Bacterial contamination during the extracorporeal circulation and bioincompatibility explain only a very small part of the high prevalence of inflammation [as defined by raised C-reactive protein (CRP)] in these patients. In the general population, several infectious agents have been implicated as likely culprits of atherosclerosis, and Chlamydia pneumoniae is the most suspected. In dialysis patients, the presence of a high titre of anti-C. pneumoniae antibodies is associated with the severity of atherosclerosis. The CREED database (Cardiovascular Risk Extended Evaluation in Dialysis patients) has on file 278 patients tested for C. pneumoniae and followed-up for 4 years. Interestingly, in this database, the risk for cardiovascular death is approximately 4 times higher in the group of patients (n=50) seropositive for Chlamydia and with raised CRP than in those with no evidence of Chlamydia infection and normal CRP. Yet seropositivity to Chlamydia did not significantly increase the risk associated with raised CRP. These data suggest that raised CRP and C. pneumoniae seropositivity is a high risk situation, but it remains very uncertain as to whether Chlamydia infection per se contributes to the high cardiovascular risk of dialysis patients.