title: In vivo activities of simulated human doses of cefepime and cefepime-AAI101 against multidrug-resistant Gram-negative Enterobacteriaceae.
abstract: The combination of cefepime with AAI101, a novel extended-spectrum β-lactamase inhibitor, possesses potent in vitro activity against many resistant Gram-negative pathogens. Against a panel of 20 mostly carbapenemase-producing cefepime-nonsusceptible strains of the family Enterobacteriaceae, we evaluated the MICs of cefepime in the presence of various fixed AAI101 concentrations (1, 2, 4, 8, and 16 mg/liter) and the in vivo efficacy of simulated human doses of cefepime and cefepime-AAI101 in a neutropenic murine thigh infection model. At 2 h after inoculation, mice were dosed with regimens that provided a profile mimicking the free drug concentration-time profile observed in humans given cefepime at 2 g every 8 h (q8h; as a 30-min infusion) or cefepime-AAI101 at 2 g/0.5 g q8h (as a 30-min infusion). Efficacy was determined by calculation of the change in thigh bacterial density (log10 number of CFU) after 24 h relative to the starting inoculum (0 h). After 24 h, bacterial growth of 2.7 ± 0.1 log10 CFU (mean ± standard error) was observed in control animals. Efficacy for cefepime monotherapy was observed against only 3 isolates, whereas increases in bacterial density similar to that in the control animals were noted for the remaining 17 strains (all with cefepime MICs of ≥ 64 mg/liter). The humanized cefepime-AAI101 dosing regimen resulted in bacterial reductions of ≥ 0.5 log10 CFU for 12 of the 20 strains. Evaluation of efficacy as a function of the fraction of the dosing interval during which free drug concentrations were above the MIC determined with different fixed concentrations of AAI101 suggested that a fixed concentration of 8 mg/liter AAI101 is most predictive of in vivo activity for the studied regimen.
authors.affiliation: Center for Anti-Infective Research and Development, Hartford Hospital, Hartford, Connecticut, USA.
authors.forename: Jared L
authors.initials: JL
authors.lastname: Crandon
authors.affiliation: Center for Anti-Infective Research and Development, Hartford Hospital, Hartford, Connecticut, USA Division of Infectious Diseases, Hartford Hospital, Hartford, Connecticut, USA david.nicolau@hhchealth.org.
authors.forename: David P
authors.initials: DP
authors.lastname: Nicolau
mesh_terms: D000818:Animals; D000077723:Cefepime; D002511:Cephalosporins / Q000627:therapeutic use*; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000472:pathogenicity*; D004756:Enterobacteriaceae Infections / Q000188:drug therapy*; D005260:Female; D006801:Humans; D051379:Mice; D008826:Microbial Sensitivity Tests; D065093:beta-Lactamase Inhibitors / Q000627:therapeutic use*
chemical_list: D002511:Cephalosporins; D065093:beta-Lactamase Inhibitors; D000077723:Cefepime