Clinical Citations: Comparing antibiotic efficacy in patients with Legionella pneumonia

Although pneumonia caused by Legionella pneumophila continues to be associated with significant morbidity, recent studies indicate that the mortality rate has declined. Two studies from Spain support this observation and suggest that therapy with levofloxacin may be more effective than therapy with erythromycin or clarithromycin.

Mykietiuk and associates studied 139 immunocompetent adults who had community-acquired pneumonia (CAP) caused by L pneumophila, from 1995 through 2003. Most of the patients (120) received appropriate initial therapy, which consisted of a macrolide (erythromycin in 53, clarithromycin in 27) or levofloxacin (in 40).

Patients who received levofloxacin had a faster time to defervescence and to clinical stability, compared with those who received a macrolide (Table). Patients who received levofloxacin also had a shorter duration of hospitalization. The groups did not differ with respect to the incidence of complications or the case-fatality rate. The complication rate was 25%, and the overall case-fatality rate was 5%. No patients died during the last 3 years of the study.

The authors note that the diagnostic evaluation of patients with CAP, including the use of urinary antigen testing, did not change significantly during the study period. However, after 1998, levofloxacin progressively replaced macrolides as the initial therapy.

Garrido and associates conducted a nonrandomized study of 292 patients with Legionella pneumonia during an outbreak in Spain. Hospitalized patients received either levofloxacin or clarithromycin. For outpatient therapy, azithromycin was also available.

Among patients with mild to moderate pneumonia, there were no significant differences between levofloxacin and macrolides with respect to clinical outcome. However, among patients with severe pneumonia, those who received levofloxacin had fewer complications (3.4%) than those who received clarithromycin (27.2%). They also had a significantly shorter mean hospital stay (5 days vs 11.3 days). The treatment groups did not differ with respect to the incidence of side effects.

The study also compared levofloxacin monotherapy with the combination of rifampicin and levofloxacin, and found no differences in outcomes.

Because the above-described studies were not randomized, the results should be interpreted with caution. Moreover, conclusions about other macrolides, such as azithromycin, cannot be made on the basis of these two studies.