title: In vitro activities of a streptogramin (RP59500), three macrolides, and an azalide against four respiratory tract pathogens.
abstract: Broth microdilution tests were carried out with 2,671 respiratory tract isolates from 19 medical centers throughout the continental United States. The tests compared a streptogramin (RP59500) to erythromycin, dirithromycin, clarithromycin, and azithromycin against Streptococcus pneumoniae, S. pyogenes, Haemophilus influenzae, and Moraxella catarrhalis. Against macrolide-susceptible strains, the potency of RP59500 was similar to that of the macrolides: the azalide, azithromycin, was two to four times more potent against H. influenzae. The azalide and three macrolides showed nearly complete cross-resistance. At 2.0 micrograms/ml or less, the streptogramin, RP59500, was active against both macrolide-resistant and -susceptible strains of S. pneumoniae (MIC for 50% of the strains tested, 0.25 microgram/ml; MIC for 90% of the strains tested, 0.5 microgram/ml).
authors.affiliation: Clinical Microbiology Institute, Tualatin, Oregon 97062.
authors.forename: A L
authors.initials: AL
authors.lastname: Barry
authors.forename: P C
authors.initials: PC
authors.lastname: Fuchs
mesh_terms: D004917:Erythromycin / Q000494:pharmacology*; D006193:Haemophilus influenzae / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D001936:Moraxella catarrhalis / Q000187:drug effects*; D013291:Streptococcus / Q000187:drug effects*; D014769:Virginiamycin / Q000494:pharmacology*
chemical_list: D014769:Virginiamycin; C062940:quinupristin-dalfopristin; D004917:Erythromycin