In vitro activity of lomefloxacin (SC 47111 or NY-198) against isolates of Legionella spp.

The in vitro activity of lomefloxacin (SC-47111 or NY-198) was compared with those of erythromycin and rifampin against a total of 180 Legionella spp. strains isolated from nosocomial or acquired respiratory tract infections and from environmental sources. Rifampin was the most active agent tested (MIC90, 0.008 microgram/ml) against Legionella spp. However, lomefloxacin was found 2-to-4-fold more active than erythromycin against most Legionella strains tested. Against Legionella pneumophila, lomefloxacin (MIC90, 0.12 microgram/ml) was significantly more than erythromycin (MIC90, 0.5 micrograms/ml). L. pneumophila serogroup 2, 3, and 5 strains (MIC90, 0.06 micrograms/ml) were more susceptible than L. pneumophila serogroup 1, 4, 6, 7, and 8 (MIC90, 0.12 microgram/ml). L. dumoffii was the most resistant species with a MIC90 of 0.25 microgram/ml and 0.5 microgram/ml, respectively, to lomefloxacin and erythromycin. The activity of lomefloxacin was similar against the isolates obtained from patients or from environmental sources.