In vitro activity of quinupristin/dalfopristin against clinical isolates of common Gram-positive bacteria in Taiwan

The MICs of quinupristin/dalfopristin against common Gram-positive bacteria isolated from various clinical specimens at a university hospital in Taiwa n were determined by the agar dilution method. The tested bacteria included methicillin-resistant Staphylococcus aureus (MRSA), methicillin-susceptibl e S. aureus (MSSA), methicillin-resistant Staphylococcus epidermidis (MRSE) , methicillin-susceptible S. epidermidis (MSSE), Streptococcus pyogenes, St reptococcus pneumoniae, and Enterococcus faecalis. With the exception off. faecalis all bacteria were susceptible to quinuprisin/dalfopristin. The MIC 50 and MIC90 were, respectively, 0.25 mu g/mL and 0.5 mu g/mL for both MRSA and MSSA; 0.25 mu g/nL and 0.5 mu g/mL for MRSE; 0.25 mu g/mL and 0.25 mu g/mL for MSSE; 0.125 mu g/mL and 0.125 mu g/mL or S. pyogenes; and less tha n or equal to 0.03 mu g/mL and 0.25 mu g/mL for S. pneumoniae. Eighty-two p ercent of the tested E. faecalis isolates were intermediately resistant or resistant to quinupristin/dalfopristin, with an MIC50 of 2 mu g/mL and an M IC90 of 4 mu g/mL. Quinupristin/dalfopristin seems to be a promising antimi crobial agent against common Gram-positive bacteria other than E. faecalis in Taiwan. (C) 1999 Elsevier Science Inc.