Abstract: Objective To set up a rapid detective technique for amikacin (Am) resistance inMycobacterium tuberculosis( M .TB) by phage amplified biologically (PhaB) assay, and to evaluate its value for application in clinical isolates.  Methods The different concentrations of M .TB and Am were screened to obtain the best conditions in PhaB assay. Am susceptibility of 108 M .TB clinical isolates were detected by PhaB assay and compared with the Results from Bactec MGIT 960. If the Results of two Methods were different, the MICs of strains were detected.  Results The best test conditions of PhaB assay were that 10^-3 mg/ml of M .TB and 2 μg/ml of amikacin were mixed and incubated at 37 ℃ for 48 hours．Of 108 M .TB clinical isolates, 82 were sensitive and 26 were resistant to Am by PhaB assay; while 80 were sensitive and 28 were resistant to Am by Bactec MGIT 960. When Bactec MGIT 960 was used as the control，the sensitivity，specificity, PPV, NPV and accuracy of PhaB assay were 89.3%, 98.8%, 96.2%, 96.3%, 96.3%, respectively.  Conclusions The PhaB assay only need 3 days. It is a highly sensitive, specific, accurate, simple and low-cost method for the rapid Am susceptibility test of M .TB isolates.

Key words: Mycobacterium tuberculosis, amikacin, microbial sensiti dity test, bacteriophages