Comparison of agar dilution, microdilution, Etest and disc diffusion to test the activity of trovafloxacin against Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus and Streptococcus pneumoniae

Abstract

To investigate the ability of four in-vitro methods to test trovafloxacin activity, this study evaluated susceptibility of 101 isolates of each of Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus and Streptococcus pneumoniae to trovafloxacin by agar dilution, microdilution, Etest and disc diffusion methodologies. MIC50 and MIC90 values were very similar for all three species with all four methods. For S. aureus and P. aeruginosa, good correlation was obtained between breakpoints of ≥ 17 mm, 14-16 mm and ≤ 13 mm with agar and microdilution MICs. For both species, Etests yielded susceptibility rates lower than the other three methods. For pneumococci, excellent correlation was obtained with all four methods.