IN-VITRO ACTIVITY OF QUINUPRISTIN DALFOPRISTIN (RP-59500) AGAINST A LARGE COLLECTION OF INFREQUENTLY ISOLATED OR TESTED SPECIES/

Quinupristin/dalfopristin (RP 5900, Synercid(R)) is a parenteral strep togramin combination antimicrobial that possesses a synergistic and of ten bactericidal action against many Gram-positive species. In this st udy, a collection of 1270 uncommonly isolated or tested strains were e valuated for susceptibility to quinupristin/dalfopristin using agar di lution minimum inhibitory concentration (MIC) methods described in the National Committee for Clinical Laboratory Standards. The greatest an timicrobial activity observed for quinupristin/dalfopristin was agains t staphylococci, streptococci, the pathogenic neisseria, Legionella sp p., Lactobacillus spp., and Peptostreptococcus spp. (MIC(90) range, 0. 5-2 mu g/ml). Marginal activity (MIC(90)s, 4 to 8 mu g/ml) was identif ied for the rarer enterococci, Leuconostoc spp., Pediococcus spp., and Streptococcus bovis. Against Haemophilus parainfluenzae, Bacteroides thetaiotaomicron, Fusobacterium spp., and Prevotella spp., the strepto gramin was inactive. Although no susceptible breakpoint has been appro ved for quinupristin/dalfopristin, three possible breakpoints (less th an or equal to 1, less than or equal to 2, or less than or equal to 4 mu g/mL) were evaluated. Acceptance of the lower breakpoints (less tha n or equal to 1 or less than or equal to 2 mu g/mL) would limit quinup ristin/dalfopristin use to staphylococci, streptococci, gonococci, men ingococci, and Legionella spp. These results markedly expand the under standing of the usable spectrum of quinupristin/dalfopristin. (C) 1996 Elsevier Science Inc.