Evaluation of the Micur microdilution systems for antibiotic susceptibility testing of gram-negative and gram-positive bacteria.

Two commercial systems for testing the antimicrobial susceptibility of bacteria were evaluated in a collaborative study at two sites using 306 freshly isolated clinical strains. Gram-negative bacteria were tested with the Micur RST 02 and gram-positive bacteria with the Micur RST 03, systems for MIC titration. For categorization of bacterial susceptibility into sensitive, intermediate or resistant, the Micur ST 02 and 03 were used for gram-negative and gram-positive bacteria respectively. The broth microdilution technique served as reference method. A total of 3672 MIC pairs were determined. MICs obtained with the Micur RST 02/03 were found to be 96.9% in agreement (+/- one log2 dilution) with the reference method results. The inter-laboratory and intra-laboratory reproducibility for the Micur RST tested with four ATCC reference strains was 97.5% and 98.5% respectively. Categorization of bacterial susceptibility with the Micur ST 02/03 agreed with 94.9% of the Micur RST results and 91.6% of the reference method results. On account of their accuracy, reproducibility and long shelf-life the Micur RST and ST systems offer a convenient method for testing antimicrobial susceptibility of bacteria in the clinical microbiology laboratory.