Detection of Chlamydia pneumoniae but not Helicobacter pylori in atherosclerotic plaques of aortic aneurysms

Recent reports suggest an association between Chlamydia pneumoniae and Helicobacter pylori bacteria and atherosclerosis. We studied 51 patients (mean age, 68.3 years) who underwent abdominal aortic aneurysm surgery. For each patient we performed a microimmunofluorescence test for immunoglobulin G (lgG), lgA, and lgM antibodies to C. pneumoniae specific antigen (TW-183). Anti-H. pylori antibodies were determined by means of an EIA-G test. Each aortic aneurysm surgical specimen was sampled into multiple sections of 0.3 cm² each and frozen at -21°C. Two samples of each aneurysm were used for a nested PCR with two sets of C. pneumoniae and two sets of H. pylori specific primers. Specimens were treated with a solution containing 20 mM Tris-HCl, Tween 20-Nonidet P-40 (0.5% [vol/vol each), and 100 μg of proteinase K per ml and incubated at 60°C for 1 h and at 98°C for 10 min. DNA was extracted twice with phenol-chloroform-isoamylic alcohol and precipitated with sodium acetate-ethanol by standard methods. Forty-one patients were seropositive for C. pneumoniae with past-infection patterns in 32 patients (16 ≤ IgG <512; 32 ≤ gA <256) and high antibody liters in 9 patients (IgG ≤ 512). In 26 of 51 patients, C. pneumoniae DNA was detected in aortic aneurysm plaque specimens. Of these patients, 23 had a serologic past-infection pattern, 2 had an acute reinfection pattern, and 1 was seronegative. Forty-seven of 51 patients were seropositive for H. pylori. In all cases PCR showed no evidence of H. pylori presence in plaque specimens. This study provides data on a possible C. pneumoniae involvement in the pathogenesis of aortic aneurysm and additional evidence for an association between this agent and atherosclerosis. Conversely, notwithstanding a high H. pylori seroprevalence observed, our results tend to rule not the possibility of a direct involvement of H. pylori in atherosclerosis.