Antimicrobial activity of quinupristin/dalfopristin, a new injectable streptogramin with a wide Gram-positive spectrum.Int J Antimicrob Agents. 1999 Sep; 13(1):21-8.IJ
Quinupristin/dalfopristin (Synercid) is a new injectable streptogramin antibiotic proposed for the treatment of severe antimicrobial infections, that has been shown to be active against Gram-positive, multi-resistant cocci. We compared the in vitro activity of quinupristin/dalfopristin with that of amoxycillin, ampicillin, penicillin, cefixime, ceftriaxone, clindamycin, erythromycin, imipenem, meropenem, oxacillin, piperacillin/tazobactam, teicoplanin and vancomycin. The susceptibility of 37 Staphylococcus aureus (14 MS, 23 MR), 26 Staphylococcus epidermidis (16 MS, 10 MR), 20 Streptococcus pneumoniae, 33 Group A Streptococcus pyogenes, 15 Streptococcus agalactiae, 10 Enterococcus faecalis (1 vancomycin-resistant), 15 Enterococcus faecium (9 van A) was evaluated. Quinupristin/dalfopristin was active against all Gram-positive species tested, including met-R S. aureus (MIC < or = 2 mg/l), met-R S. epidermidis (MIC < or = 2 mg/l), S. pneumoniae (MIC < or = 1 mg/l), ery-R and ery-S streptococci (MIC < or = 1 mg/l). The strains of E. faecalis were generally less susceptible. Time-kill studies confirmed that quinupristin/dalfopristin at 4 x MIC concentration showed a complete bactericidal effect (3 log reduction) in about 4 6 h against all strains tested. A post-antibiotic effect (PAE) of 3.9-5.2 h was observed at 4 x MIC concentration of quinupristin/dalfopristin against staphylococci. A prolonged PAE was obtained for S. pneumoniae (8 h), S. pyogenes (9 h) and S. agalactiae (7 h), while the shortest PAE was seen for E. faecalis and E. faecium (about 4 h).