Antimicrobial Chemotherapy for Legionnaires Disease: Time for a Change

Erythromycin became the de facto standard of treatment for Legionnaires disease soon after the first recognized epidemic of this disease occurred 22 years ago [1, 2]. However, it is now time for a change in therapy because of increasing evidence of the superiority of newer antimicrobial agents. The conclusion that erythromycin is the drug of choice for Legionnaires disease was based on unavoidably imperfect retrospective analysis of treatment outcomes from the epidemic, which showed the lowest overall fatality rates with either erythromycin or tetracycline therapy. No prospective comparative studies with adequate statistical power of the treatment of Legionnaires disease have been published. Because of the relative rarity of Legionnaires disease and its widely varying outcomes, it is unlikely that an adequate comparative clinical trial of the disease will ever be completed; such a study would need to have 300 to 900 patients with the disease in each experimental group to have adequate statistical power [3]. This means that decisions about new therapy must be based on laboratory experiments and limited clinical data.

Case-fatality rates for treated Legionnaires disease depend on various factors, but the chief determinants seem to be 1) the premorbid immune and general health status of the patient and 2) whether the disease is community-acquired or nosocomial [3-6]. Higher fatality rates for nosocomial infection are probably due to host-related rather than organism-related factors. Previously healthy patients with community-acquired Legionnaires disease who do not require hospitalization respond well to erythromycin therapy about 95% to 99% of the time. Quite a different picture emerges for immunocompromised patients with Legionnaires disease or for patients with nosocomial Legionnaires disease. Fatality rates of up to …