COMPARISON OF THE E-TEST AND A PROPORTION DILUTION METHOD FOR SUSCEPTIBILITY TESTING OF MYCOBACTERIUM-TUBERCULOSIS

Minimal inhibitory concentrations (MICs) of amikacin, streptomycin, fu sidic acid, rifampicin, clarithromycin, ciprofloxacin, ofloxacin, and fleroxacin were determined by the E test for 20 strains of Mycobacteri um tuberculosis. The resulting discrimination in resistant or sensitiv e strains was compared with the results of an extended proportion dilu tion method. There were no more than three strains per antibiotic with different ratings with the exception of ciprofloxacin and ofloxacin. In these discrepant cases, the breakpoint concentrations had a positio n at the top of the rest strip, which may be unfavourable for MIC read ing. The MICs of streptomycin (1-2 mg/l) and rifampicin (2-4 mg/l) for the control strain M. tuberculosis H37Rv (ATCC 27294) were close to t he reference values according to the German standard DIN 58943. It is concluded that the E test is suitable for susceptibility testing of sl owly growing M. tuberculosis isolates.