Determination of moxifloxacin anaerobic susceptibility breakpoints according to the Clinical and Laboratory Standards Institute guidelines

A summary of the key data presented to Clinical and Laboratory Standards Institute (CLSI, formerly National Committee for Clinical and Laboratory Standards) in determination of moxifloxacin anaerobic breakpoints is presented. The breakpoint analysis required review of a variety of data, including bacteriologic and clinical outcomes by MIC of anaerobic isolates from prospective clinical trials in patients with complicated intra-abdominal infections, human and animal pharmacokinetic/pharmacodynamic (PK/PD) information and in vitro models, MIC distributions of indicated organisms, and animal model efficacy data for strains with MIC values around prospective breakpoints. The compilation of the various components of this breakpoint analysis supports the US Food and Drug Administration (FDA) and CLSI moxifloxacin anaerobic breakpoints of ≤2 mg/L (susceptible), 4 mg/L (intermediate), and ≥8 mg/L (resistant), and provides information to European investigators for interpretation of MICs prior to establishment of the European Committee on Antimicrobial Susceptibility Testing breakpoints.