[Reliability of bioluminescent assay (ATP method) for testing antimicrobial susceptibility of Mycobacterium...

To evaluate the reliability of our previously reported antimicrobial susceptibility test by ATP method, we have compared our ATP method to the reference test methods such as Mycobacteria Growth Indicator Tube(MGIT) method, minimum inhibitory concentration(MIC) method, NCCLS M24-T agar proportion method(M24-T method), and Vite spectrum method. The concentrations of drugs used for the assessment were isoniazid(INH) 0.1 microgram/ml, rifampicin(RFP) 2.0 micrograms/ml, ethambutol(EB) 2.5 micrograms/ml, streptomycin (SM) 2.0 micrograms/ml, and kanamycin (KM) 5.0 micrograms/ml. When six M. tuberculosis ATCC strains were subjected to 6 independent experiments by using ATP method, highly reproducible results were obtained on the fifth day of the incubation. We examined correlation among ATP method and reference test methods in drug susceptibility testing for 65 clinical isolates of M. tuberculosis. The correlation between ATP method and MGIT-, MIC-, M24-T method were more than 95% for all drugs. When ATP method and Vite spectrum method was compared, the correlation was 87.7% for INH, 98.5% for RFP, 90.8% for EB, 92.3% for SM, 96.9% for KM. The culture period for determining susceptibility between ATP method and MGIT method was compared by using ATCC reference strains and clinical isolates. Six M. tuberculosis ATCC strains were subjected to 6 independent experiments. By the MGIT method, 8 days were required to obtain the results, whereas 3 days were enough by the ATP method. For 65 clinical isolates, the MGIT method required 9 days for determining susceptibility of all isolates. The ATP method required only 5 days for the same strains. These data demonstrate that the improved ATP method that we reported, is simple, rapid, highly reproducible and nonradiometric, and could be used for the assessment of drug susceptibility for M. tuberculosis with high reliability.