Quinupristin-dalfopristin resistance among gram-positive bacteria in Taiwan

To understand quinupristin-dalfopristin resistance among clinical isolates of gram-positive bacteria in Taiwan, where this agent is not yet available for clinical use, we evaluated 1,287 nonduplicate isolates recovered from J anuary 1996 to December 1999 for in vitro susceptibility to quinupristin-da lfopristin and other newer antimicrobial agents. All methicillin-susceptibl e Staphylococcus aureus (MSSA) isolates were susceptible to quinupristin-da lfopristin. High rates of nonsusceptibility to quinupristin-dalfopristin (M ICs, greater than or equal to 2 mug/ml) were demonstrated for the following organisms: methicillin resistant S. aureus (MRSA) (31%), coagulase-negativ e staphylococci (CoNS) (16%), Streptococcus pneumoniae (8%), viridans group streptococci (51%), vancomycin- susceptible enterococci (85%), vancomycin- resistant Enterococcus faecalis (100%), vancomycin-resistant Enterococcus f aecium (66%), Leuconostoc spp. (100%), Lactobacillus spp. (50%), and Pedioc occus spp. (87%). All isolates of MSSA, MRSA, S. pneumoniae, and viridans g roup streptococci were susceptible to vancomycin and teicoplanin. The rates of nonsusceptibility to vancomycin and teicoplanin were 5 and 7%, respecti vely, for CoNS, ranging from 12 and 18% for S. simulans to 0 and 0% for S. cohnii and S. auricularis. Moxifloxacin and trova-floxacin had good activit ies against these isolates except for ciprofloxacin-resistant vancomycin re sistant enterococci and methicillin-resistant staphylococci. In Taiwan, vir giniamycin has been used in animal husbandry for more than 20 years, which may contribute to the high rates of quinupristin-dalfopristin resistance.