Comparison of the in vitro activity of pristinamycin and quinupristin/dalfopristin against Streptococcus pneumoniae

The in vitro activity of quinupristin/dalfopristin, a new injectable strept ogramin, and pristinamycin was evaluated against 200 recently isolated clin ical Streptococcus pneumoniae strains expressing various degrees of suscept ibility to penicillin G and erythromycin. MICs were determined by the agar dilution method. All strains were susceptible to pristinamycin irrespective of their susceptibility to penicillin G or erythromycin (MIC90: 0.25 mg/L for each phenotype). The activity of quinupristin/dalfopristin was slightly lower than that of pristinamycin against 42 penicillin G-susceptible/eryth romycin-susceptible strains (MIC90: 0.5 mg/L), 13 penicillin G-susceptible/ erythromycin-resistant strains (MIC90: 1 mg/L), 25 penicillin G-intermediat e or -resistant/erythromycin-susceptible strains (MIC90: 0.5 mg/L) and 120 penicillin G-intermediate or -resistant/erythromycin-resistant strains (MIC 90: 0.5 mg/L). The activity of both streptogramins was not significantly al tered in case of erythromycin resistance. Thus, both streptogramins might b e useful for the treatment of pneumococcal infections, especially in cases of multiresistant strains. (C) 2000 Editions scientifiques et medicales Els evier SAS.