title: RO 23-9424, a new cephalosporin 3'-quinolone: in-vitro antimicrobial activity and tentative disc diffusion interpretive criteria.
abstract: The susceptibility of 410 clinical bacterial isolates to RO 23-9424, a novel cephalosporin 3'-quinolone, was determined. Overall, 97% of Enterobacteriaceae and 100% of staphylococci were inhibited by < or = 8.0 mg/L of RO 23-9424. Only 60% of Pseudomonas aeruginosa and 80-90% of Pseudomonas spp. and Xanthomonas maltophilia were inhibited by this concentration. Enterococci and Listeria monocytogenes were resistant to RO 23-9424. Clinical isolates of Moraxella catarrhalis, Streptococcus spp., and Corynebacterium jekeium were all susceptible to < or = 8.0 mg/L of RO 23-9424. This drug's antimicrobial activity was superior to that of its two components fleroxacin and desacetylcefotaxime against the organisms tested. Using < or = 8.0 mg/L and > or = 32 mg/L respectively as the susceptible and resistant MIC breakpoints for RO 23-9424, the regression analysis-derived disc diffusion zone diameter breakpoints for the 30 micrograms disc are: susceptible > or = 19 mm, intermediate 16-18 mm, and resistant < or = 15 mm.
authors.affiliation: Department of Pathology, Oregon Health Sciences University, Portland 97201.
authors.forename: M A
authors.initials: MA
authors.lastname: Pfaller
authors.forename: A L
authors.initials: AL
authors.lastname: Barry
authors.forename: P C
authors.initials: PC
authors.lastname: Fuchs
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects*; D001431:Bacteriological Techniques; D002439:Cefotaxime / Q000031:analogs & derivatives* / Q000494:pharmacology; D016576:Fleroxacin / Q000031:analogs & derivatives* / Q000494:pharmacology; D024841:Fluoroquinolones; D008826:Microbial Sensitivity Tests; D012044:Regression Analysis
chemical_list: D000890:Anti-Infective Agents; D024841:Fluoroquinolones; C060441:Ro-23-9424; C029281:desacetylcefotaxime; D002439:Cefotaxime; D016576:Fleroxacin