Antibiotics for bacteremic pneumonia: Improved outcomes with macrolides but not fluoroquinolones

The questions of whether the use of antibiotics that are active against atypical organisms is beneficial in the treatment of community-acquired pneumonia and of the potential mechanisms of any beneficial effects remain unresolved. Proposed mechanisms include activity against atypical organisms vs the immunomodulatory effects of these antibiotics. The study of outcomes of a large cohort of patients with bacteremic pneumonia provides a unique opportunity to address these questions by excluding patients with primary atypical infection.

We reviewed data from the charts of 2,209 Medicare patients who were admitted to hospitals across the United States from either home or a nursing facility with bacteremic pneumonia between 1998 and 2001. Patients were stratified according to the type of antibiotic treatment. Multivariate modeling was performed to assess the relationship between the class of antibiotic used and several outcome variables.

The initial use of any antibiotic active against atypical organisms was independently associated with a decreased risk of 30-day mortality (odds ratio [OR], 0.76; 95% confidence interval [CI], 0.59 to 0.98; p = 0.03) and hospital admission within 30 days of discharge (OR, 0.67; 95% CI, 0.51 to 0.89; p = 0.02). Further analysis revealed that the benefits of atypical treatment were associated with the use of macrolides, but not the use of fluoroquinolones or tetracyclines, with macrolides conferring lower risks of in-hospital mortality (OR, 0.59; 95% CI, 0.40 to 0.88; p = 0.01), 30-day mortality (OR, 0.61; 95% CI, 0.43 to 0.87; p = 0.007), and hospital readmission within 30 days of discharge (OR, 0.59; 95% CI, 0.42 to 0.85; p = 0.004).

Initial antibiotic treatment including a macrolide agent is associated with improved outcomes in Medicare patients hospitalized with bacteremic pneumonia. These results have implications regarding the mechanism by which the use of a macrolide for treatment of pneumonia is associated with improved outcomes.