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.