The in-vitro activity of ceftibuten was compared with cefuroxime and cefadroxil against 475 clinically-significant, epidemiologically-distinct isolates of Gram-negative bacilli: 170 from blood, 212 from urine and 93 from a supplementary collection of multiply-resistant strains known to have resistance plasmids, to have caused sporadic or epidemic nosocomial infection, or both. Ceftibuten MICs ranged from 0·003 to >32mg/l, with a modal MIC of 0·01 mg/l: 95% of all isolates had ceftibuten MIC values of ≤8 mg/l, the sensitivity breakpoint suggested by the manufacturer. Ninety per cent of isolates had MICs of ≤ 1 mg/l and 49% had MICs of ≤ 0·03 mg/l. All isolates of Klesiella, Serratia, Proteus and Providencia spp., and Morganella morganii had MIC values of 8 mg/l or less. Only two of 124 isolates of Escherichia coli tested, and only one of 23 Citrobacter spp., had MICs of > 8 mg/l (16, 16 and > 32 mg/l respectively). Resistance (MIC > 16 mg/l) was more frequent among /l and Acinetobacter spp. Thirteen of 52 Enterobacter spp., and seven of 18 Acinetobacter calcoaceticus had MICs of at least 32 mg/l. MIC ranges, modal MICs and MIC90s indicated that ceftibuten was, with the exception of only two strains, consistently more active in-vitro than cefuroxime, which was in turn more active than cefadroxil. © 1990 The British Society for Antimicrobial Chemotherapy.
