Antibiotic treatment of guinea-pigs infected with agent of Legionnaires' disease.

Erythromycin and rifampicin (rifampin) were able to prevent death of guineapigs given intraperitoneal injections of the agent causing legionnaires' disease. Penicillin, chloramphenicol, tetracycline, and gentamicin showed no significant effect. On the basis of clinical experience and experimental observations, erythromycin is recommended for patients suspected to have legionnaires' disease. Combined therapy with erythromycin and rifampicin may be justified in patients with confirmed legionnaires' disease who are not responding to erythromycin alone or as part of a controlled antibiotic trial among suspected cases during an outbreak of legionnaires' disease.