title: Timed killing kinetic studies of the interaction between ciprofloxacin and beta-lactams against gram-negative bacilli.
abstract: Timed killing kinetic studies were performed with ciprofloxacin in combination with aztreonam, ceftazidime, piperacillin/tazobactam, and ticarcillin/clavulanic acid against three isolates each of Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens, and Pseudomonas aeruginosa. Each antimicrobial agent in the combination was tested at its MIC and at one-half and one-quarter of its MIC. Colony counts were determined at 0, 3, 5, and 7 hours. Synergy occurred most frequently at 7 hours and, when present, was most likely to occur when ciprofloxacin and the beta-lactam were tested at concentrations equal to their respective MICs. Synergy after 3 hours of incubation was not predictive of a synergestic interaction at 5 or 7 hours. Antagonism was noted in several instances, particularly when ciprofloxacin and the beta-lactam were combined at one-quarter of their respective MICs.
authors.affiliation: Department of Clinical Pathology, Cleveland Clinic Foundation, OH 44195-5140, USA.
authors.forename: J K
authors.initials: JK
authors.lastname: Pohlman
authors.forename: C C
authors.initials: CC
authors.lastname: Knapp
authors.forename: M D
authors.initials: MD
authors.lastname: Ludwig
authors.forename: J A
authors.initials: JA
authors.lastname: Washington
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001398:Aztreonam / Q000494:pharmacology; D002442:Ceftazidime / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology; D002939:Ciprofloxacin / Q000494:pharmacology*; D019818:Clavulanic Acid; D002969:Clavulanic Acids / Q000494:pharmacology*; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D016972:Enterobacter cloacae / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007700:Kinetics; D007711:Klebsiella pneumoniae / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D008997:Monobactams / Q000494:pharmacology; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D010406:Penicillins / Q000494:pharmacology; D010878:Piperacillin / Q000494:pharmacology; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D012706:Serratia marcescens / Q000187:drug effects*; D000078142:Tazobactam; D013982:Ticarcillin / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D002511:Cephalosporins; D002969:Clavulanic Acids; D004791:Enzyme Inhibitors; D008997:Monobactams; D010406:Penicillins; D019818:Clavulanic Acid; D002939:Ciprofloxacin; D010397:Penicillanic Acid; D002442:Ceftazidime; D013982:Ticarcillin; D001398:Aztreonam; D000078142:Tazobactam; D010878:Piperacillin