Clinical Question: In patients who have experienced a myocardial infarction (MI), is antibiotic therapy aimed at eradicating Chlamydia pneumoniae infection effective in preventing a second coronary event?

Setting: Outpatient (any)

Study Design: Meta-analysis (randomized controlled trials)

Synopsis: The authors of this meta-analysis searched several databases to find English language, randomized controlled trials of antibiotic therapy directed against C. pneumoniae infection that evaluated a clinical outcome. Nine studies met their criteria, and more than 12,000 patients were enrolled.

All of the studies used a macrolide antibiotic as the primary intervention, with one study also using a triple therapy of azithromycin, metronidazole, and omeprazole to eradicate Helicobacter pylori infection. All patients had acute coronary syndrome or coronary heart disease and were not selected based on the presence of high C. pneumoniae titers. Duration of treatment ranged from three days to three months.

Overall, antibiotic treatment did not reduce the risk of experiencing any coronary event, MI, angina, or mortality. However, the investigators combined studies using a wide range of antibiotic dosages, including azithromycin for a total of five days, once-weekly azithromycin for three months, or clarithromycin or roxithromycin daily for 28 to 90 days. It is possible that higher dosages or longer treatment durations could produce a clinically relevant effect.

Bottom Line: Antibiotic therapy with a macrolide, aimed at eradicating C. pneumoniae infection, is ineffective at reducing the recurrence of a coronary event or decreasing mortality in patients who have had an MI or acute coronary syndrome. (Level of Evidence: 1a)