Progression of early carotid atherosclerosis is only temporarily reduced after antibiotic treatment of Chlamydia pneumoniae seropositivity.

BACKGROUND: Chlamydia pneumoniae (Cp) infection has been associated with atherosclerosis and cardiovascular events. There are controversial results regarding the beneficial effects of antibiotic therapy on future cardiovascular end points.

METHODS AND RESULTS: We determined the long-term effect of a 30-day roxithromycin therapy on intima-to-media thickness (IMT) progression of the common carotid artery in 272 consecutive Cp-positive and Cp-negative patients with ischemic stroke in a prospective, double-blind, randomized trial with a follow-up of 4 years. Cp IgG (> or =1:64) or IgA (> or =1:16) antibodies were initially found in 125 (46%) patients. During the 3 years before antibiotic therapy, Cp-positive patients showed an enhanced IMT progression even after adjustment for other cardiovascular risk factors (0.12 [0.11 to 0.14] versus 0.07 [0.05 to 0.09] mm/year; P<0.005). The 62 Cp-positive patients given roxithromycin showed a reduced IMT progression during the first 2 years compared with the Cp-positive patients without therapy (0.07 [0.045 to 0.095] versus 0.11 [0.088 to 0.132] mm/year; P<0.01). However, IMT progression increased again during the third and fourth year to similar values as before treatment. No significant difference in the occurrence of future cardiovascular events was found between both groups during follow-up.

CONCLUSIONS: The only limited positive impact of antibiotic therapy on early atherosclerosis progression in Cp-positive patients observed in our study may explain the negative results of most antibiotic trials on clinical end points.