Antimicrobial activity of quinupristin/dalfopristin, a new injectable streptogramin with a wide Gram-positive spectrum

Quinupristin/dalfopristin (Synercid) is a new injectable streptogramin anti biotic proposed for the treatment of severe antimicrobial infections, that has been shown to be active against Gram-positive, multi-resistant cocci. W e compared the in vitro activity of quinupristin/dalfopristin with that of amoxycillin, ampicillin, penicillin, cefixime, ceftriaxone, clindamycin, er ythromycin, imipenem, meropenem, oxacillin, piperacillin/tazobactam, teicop lanin and vancomycin. The susceptibility of 37 Staphylococcus aureus (14 MS , 23 MR), 26 Staphylococcus epidermidis (16 MS, 10 MR), 20 Streptococcus pn eumoniae, 33 Group A Streptococcus pyogenes, 15 Streptococcus agalactiae, 1 0 Enterococcus faecalis (1 vancomycin-resistant), 15 Enterococcus faecium ( 9 van A) was evaluated. Quinupristin/dalfopristin was active against all Gr am-positive species tested, including met-R S. aureus (MIC less than or equ al to 2 mg/l), met-R S. epidermidis (MIC less than or equal to mg/l), S. pn eumoniae (MIC I 1 mg/l), ery-R and ery-S streptococci (MIC less than or equ al to 1 mg/l). The strains of E. faecalis were generally less susceptible. Time-kill studies confirmed that quinupristin/dalfopristin at 4 x MIC conce ntration showed a complete bactericidal effect (3 log reduction) in about 4 -6 h against all strains tested. 4 post-antibiotic effect (PAE) of 3.9-5.2 h was observed at 4 x MIC concentration of quinupristin/dalfopristin agains t staphylococci. A prolonged PAE was obtained for S. pneumoniae (8 h), S. p yogenes (9 h) and S. agalactiae (7 h), while the shortest PAE was seen for E. faecalis and E. faecium (about 4 h). (C) 1999 Published by Elsevier Scie nce B.V. and International Society of Chemotherapy. All rights reserved.