Antimicrobial susceptibility testings against clinical mucoid Pseudomonas aeruginosa isolates

We compared antimicrobial susceptibility results of 19 mucoid Pseudomonas aeruginosa isolates by the MicroScan, Vitek and Raisus broth microdilution and Etest methods with those by the Clinical and Laboratory Standards Institute (CLSI) agar dilution method. Minimum inhibitory concentrations (MICs) determined by the MicroScan and Vitek broth microdilution methods showed generally essential agreement (MICs within +/- 2 log(2) dilutions) with those obtained by the CLSI reference method for antimicrobials such as piperacillin. cefepime, imipenem, meropenem and levofloxacin. Essential agreement between Etest and the reference methods were 63.2% for piperacillin, 78.9% for cefepime, 94.7% for imipenem and levofloxacin and 100% for meropenem. The Vitek and MicroScan broth microdilution methods were respectively limited for 6 and 1 isolates by inadequate turbidity associated with bacterial growth, while the Raisus system detected bacterial growth, permitting determination of MICs in all isolates.