The main causative agent of community-acquired pneumonia was and remains Streptococcus pneumoniae. At the same time, the effect of azithromycin on mortality from pneumococcal pneumonia remains uncertain. The purpose of a retrospective cohort study in the United States was to assess the relationship between survival and the use of azithromycin in pneumococcal pneumonia.

The study used data from adult patients with pneumonia caused by S. pneumoniae hospitalized in the period from January to December 2010. The diagnosis of pneumonia was made on the basis of clinical syndrome and radiological signs of the presence of infiltrative changes in the lungs.

As a primary end-point, the nosocomial mortality rate was considered. Thus, during the analysis, this indicator was compared in groups of patients who received and did not receive azithromycin. Variables that could affect the mortality rate included demographic characteristics, severity of the underlying disease, concomitant pathology, and characteristics directly related to the infection (e.g., adequacy of treatment initially prescribed, presence or 'absence of bacteremia). For an independent assessment of the effect of azithromycin on nosocomial mortality, logistic regression analysis was used.

The study cohort included 187 patients (mean age 67.0 ± 8.2 years, 50.3% were men, 5.9% of patients were admitted to the intensive care unit).

The most common antibiotics used in other groups (not macrolides) were ceftriaxone (n = 111), cefepime (n = 31) and moxifloxacin (n = 22). About 2/3 of the cohort evaluated received azithromycin.

The overall mortality rate was lower in patients receiving azithromycin (5.6% vs 23.6%, p less than 0.01). The final survival model included 4 variables: age, the need for mechanical ventilation, the adequacy of the treatment initially prescribed and the use of azithromycin. The adjusted relative risk of mortality from azithromycin was 0.26% (95% confidence interval 0.08-0.80, p = 0.018), i.e. the risk of death during treatment with azithromycin was reduced by 74 %.

Thus, with pneumonia caused by S. pneumoniae, a fairly high mortality rate remains, and the use of azithromycin in pneumococcal pneumonia results in a statistically significant increase in survival.