title: Elevated Chlamydia pneumoniae antibodies, cardiovascular events, and azithromycin in male survivors of myocardial infarction.
abstract: BACKGROUND
  The clinical significance of the association between elevated anti-Chlamydia pneumoniae (Cp) antibody titres and coronary heart disease (CHD) is unclear. We explored the relationship between antibodies against Cp and future cardiovascular events in male survivors of myocardial infarction (MI). The effect of azithromycin antibiotic therapy was assessed in a subgroup of post-MI patients.
  
  
  RESULTS
  We screened 220 consecutive male survivors of MI for anti-Cp antibodies. Of these, 213 patients were stratified into three groups: group Cp-ve (n=59), no detectable Cp antibodies; group Cp-I (n=74), intermediate titres of 1/8 to 1/32 dilution; and group Cp+ve (n=80), seropositive at > or = 1/64 dilution. Patients with persisting seropositivity of > or = 1/64 were randomized to either oral azithromycin (Cp+ve-A, 500 mg/d for 3 days [n=28] or 500 mg/d for 6 days [n=12]) or placebo (Cp+ve-P, n=20). Cp+ve-NR (n=20) represented patients not recruited into the antibiotic trial. The incidence of adverse cardiovascular events (over a mean follow-up period of 18+/-4 months) was recorded and shown to increase with increasing anti-Cp titre: Cp-ve, n=4 (7%); Cp-I, n=11 (15%); Cp+ve-NR, n=6 (30%); and Cp+ve-P, n=5 (25%). Cp+ve-NR and Cp+ve-P groups had a fourfold-increased risk for adverse cardiovascular events compared with the Cp-ve group (odds ratio [OR], 4.2; 95% confidence interval [CI], 1.2 to 15.5; P=.03). In contrast, the OR for cardiovascular events in patients receiving azithromycin (Cp+ve-A, single or double course) was the same as in the Cp-ve group (OR, 0.9; 95% CI, 0.2 to 4.6, P=NS). Patients receiving azithromycin were more likely to experience a decrease in IgG anti-Cp titres than were those in the placebo group (P=.02).
  
  
  CONCLUSIONS
  An increased anti-Cp antibody titre may be a predictor for further adverse cardiovascular events in post-MI patients. Taking a short course of azithromycin may lower this risk, possibly by acting against Cp.
authors.affiliation: Department of Cardiological Sciences, St George's Hospital Medical School, London, UK.
authors.forename: S
authors.initials: S
authors.lastname: Gupta
authors.forename: E W
authors.initials: EW
authors.lastname: Leatham
authors.forename: D
authors.initials: D
authors.lastname: Carrington
authors.forename: M A
authors.initials: MA
authors.lastname: Mendall
authors.forename: J C
authors.initials: JC
authors.lastname: Kaski
authors.forename: A J
authors.initials: AJ
authors.lastname: Camm
mesh_terms: D000284:Administration, Oral; D000368:Aged; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D000907:Antibodies, Bacterial / Q000097:blood*; D017963:Azithromycin / Q000008:administration & dosage*; D015415:Biomarkers; D002690:Chlamydia Infections / Q000097:blood / Q000188:drug therapy / Q000382:microbiology* / Q000503:physiopathology; D016993:Chlamydophila pneumoniae / Q000276:immunology* / Q000302:isolation & purification; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood / Q000382:microbiology* / Q000503:physiopathology
chemical_list: D000900:Anti-Bacterial Agents; D000907:Antibodies, Bacterial; D015415:Biomarkers; D017963:Azithromycin