The activities of
sparfloxacin,
ciprofloxacin, and
erythromycin for 21 clinical Legionella isolates were determined by
agar and broth dilution susceptibility testing and by growth inhibition assays in guinea pig alveolar macrophages (
sparfloxacin and
ciprofloxacin). All three
antimicrobial agents had roughly equivalent activities when buffered
charcoal yeast extract
agar medium supplemented with 0.1%
alpha-ketoglutarate was used as the test medium; the MICs for 90% of strains were 1.0 micrograms/ml for
erythromycin and
sparfloxacin and 0.5 microgram/ml for
ciprofloxacin. Buffered
charcoal yeast extract medium supplemented with 0.1%
alpha-ketoglutarate inhibited the activities of all the
antimicrobial agents tested, as judged by the susceptibility of a control Staphylococcus aureus strain. Broth macrodilution MICs for two L. pneumophila strains in buffered yeast extract supplemented with 0.1%
alpha-ketoglutarate were less than or equal to 0.03 microgram/ml for
sparfloxacin, 0.06 microgram/ml for
ciprofloxacin, and 0.25 microgram/ml for
erythromycin; only
erythromycin was inhibited by this medium.
Ciprofloxacin and
sparfloxacin (both 0.25 microgram/ml) reduced bacterial counts of two L. pneumophila strains grown in guinea pig alveolar macrophages by 2 log10 CFU/ml, but regrowth occurred over a 3-day period.
Sparfloxacin, but not
ciprofloxacin (both 1 microgram/ml), caused a 3- to 4-day postantibiotic effect. Pharmacokinetic and
therapy studies of
sparfloxacin were performed in guinea pigs with L. pneumophila
pneumonia. For the pharmacokinetic study,
sparfloxacin was given (10 mg/kg of
body weight) to infected guinea pigs by the intraperitoneal route; peak levels in serum and lung were 2.6 micrograms/ml and 1.6 micrograms/g, respectively, at 1 h, with a terminal-phase half-life of elimination from serum of 5 h.(ABSTRACT TRUNCATED AT 250 WORDS)