Comparison of spiramycin and erythromycin in the treatment of experimental guinea pig legionellosis.

Spiramycin was compared with erythromycin in a guinea pig model of severe Legionella pneumophila serogroup 1 infection. Male guinea pigs weighting 264-321 g were infected by the intraperitoneal route with 1.2 x 10(7) virulent L. pneumophila serogroup 1. Forty eight h after infection, animals that had lost greater than or equal to 9% of their body weight were randomly assigned to receive 48, 54 and 72 h after infection intraperitoneal injections of (1) distilled water (n = 20), (2) erythromycin lactobionate, 30 mg/kg per injection, (n = 22) or (3) the injectable form of spiramycin adipate, 30 mg/kg per injection (n = 22). Animals were observed daily for 15 days. All infected animals treated with distilled water died within four days of infection. Of the 22 animals treated with spiramycin, 10 (45.5%) died, and of the 22 animals treated with erythromycin, 11 (50.0%) died of disseminated L. pneumophila infection. In this animal model of very severe L. pneumophila infection, the injectable forms of erythromycin and of spiramycin gave similar results. Spiramycin should therefore be considered for the treatment of Legionnaires' disease in man.