Comparative in-vitro activity of RP 59500.

The in-vitro activity of RP 59500 was compared with that of other appropriate antibiotics against 131 staphylococci, 97 streptococci, 20 enterococci, 68 Neisseria spp., 68 Haemophilus influenzae, 21 Moraxella catarrhalis and 250 Gram-negative bacilli. RP 59500 was more active than oxacillin, vancomycin and erythromycin against staphylococci (MIC 0.03-4 mg/L). RP 59500 inhibited streptococci between 0.03-1 mg/L and enterococci between 1-8 mg/L, but was less active than ampicillin and erythromycin. However, its activity remained unchanged against strains with acquired resistance to ampicillin, erythromycin and oxacillin. It was as active as ampicillin against Neisseria spp., but less active against H. influenzae and M. catarrhalis. All enterobacteria and non-fermenters were resistant to RP 59500.