Gatifloxacin Susceptibility Testing Interpretive Criteria and Quality Control Guidelines for Dilution and Disk Diffusion Methods

Abstract

Gatifloxacin (formerly AM-1155 or CG5501) is a newer 8-methoxy fluoroquinolone with a wide spectrum of antimicrobial activity.[1-4] Among the species inhibited by gatifloxacin are selected anaerobes, Chlamydia spp., Mycoplasma pneumoniae, mycobacteria, drug-resistant Streptococcus pneumoniae andNeisseria gonorrhoeae as well as many nonfastidious, rapid-growing bacteria. Gatifloxacin has excellent bioavailability, with an elimination half-life of 7 to 8 hours and peak serum concentrations of 3.35 and 5.41 mg/L, respectively, with single 400 and 600mg doses.[5] It penetrates macrophages and will concentrate 5to 7-fold within the cell. The drug was well tolerated and the intake of food had no adverse effect on the pharmacokinetic features, which allowed advancement to human clinical trials. The risk of phototoxicity was also considered low. In this study, we report the results of testing the activity of gatifloxacin against rapidly growing aerobic pathogens by 2 methods published by the National Committee for Clinical Laboratory Standards (NCCLS) to determine interpretive criteria for antimicrobial susceptibility testing.[6,7] In addition, the quality control guidelines were established for the gatifloxacin 5μg disks and broth microdilution tests by use of a 9-laboratory trial conforming to NCCLS study design.[8]