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Efficacy of spiramycin on experimental airborne legionellosis in guinea pigs
M Nowicki1, J C Paucod, N Bornstein
1Centre National de Référence des Légionelloses, Faculté de Médecine Alexis Carrel, France.
Abstract:
The effect of preventive and curative spiramycin therapy was studied in guinea pigs infected by aerosol with the experimental model previously tested. The infectious aerosol was obtained from a virulent strain of Legionella pneumophila (Philadelphia ATCC 33 152). Male guinea pigs (Dunkin-Hartley) weighing 250-300 g were exposed for 30 min to an aerosol of 1 or 10 LD50 (10(3) or 10(4) viable inhaled organisms). Spiramycin was administered intraperitoneally (150 mg/kg/day) 18 h after infection for five days for curative therapy; for preventive therapy it was administered on the day before and on the day of aerosol administration (10 LD50). The animals were observed during seven days for weight and temperature and 28 days for survival; bacterial (lungs, spleen) and serological tests were performed. Spiramycin levels (lungs, serum) were evaluated during treatment by a microbiological method. The survival rate in the treated guinea pigs after inhalation of 1 LD50 was 100%. For the 10 LD50 aerosol, curative and preventive therapy gave a survival rate of 87.5%; these results are significant when compared with results of non-treated animals, P less than 0.05. Spiramycin merits further study in experimental and human legionellosis.
Insights
Spiramycin therapy significantly improved survival rates in guinea pigs infected with Legionella pneumophila. Both preventive and curative treatments demonstrated effectiveness against this serious bacterial infection.
Area of Science:
- * Infectious Diseases
- * Microbiology
- * Pharmacology
Background:
- * Legionella pneumophila causes Legionnaires' disease, a severe pneumonia.
- * Effective treatments for experimental legionellosis are crucial for understanding human disease progression.
- * Macrolide antibiotics like spiramycin are potential candidates for treating Legionnaires' disease.
Purpose of the Study:
- * To evaluate the efficacy of spiramycin as both a preventive and curative therapy against Legionella pneumophila infection in a guinea pig model.
- * To assess the impact of spiramycin on survival rates, clinical signs, and bacterial load in infected animals.
Main Methods:
- * Guinea pigs were infected via aerosol with virulent Legionella pneumophila (1 or 10 LD50).
- * Spiramycin was administered intraperitoneally for preventive (pre-exposure) and curative (post-exposure) therapy.
- * Survival, weight, temperature, bacterial counts (lungs, spleen), and spiramycin levels (serum, lungs) were monitored.
Main Results:
- * Spiramycin treatment resulted in a 100% survival rate at 1 LD50 exposure.
- * At 10 LD50 exposure, both preventive and curative spiramycin therapy achieved an 87.5% survival rate.
- * Treated animals showed significantly higher survival rates compared to untreated controls (P < 0.05).
Conclusions:
- * Spiramycin demonstrates significant therapeutic potential in preventing and treating experimental Legionella pneumophila infection in guinea pigs.
- * The findings support further investigation of spiramycin for managing human legionellosis.
- * Spiramycin exhibits promising efficacy in a relevant animal model of Legionnaires' disease.