Evaluation of mycobacteria growth indicator tube [MGIT] for drug susceptibility testing of mycobacterium tuberculosis

ABSTRACT

The importance of rapid availability of Mycobacterium tuberculosis [M. tuberculosis] antimicrobial susceptibility testing results is universally acknowledged. This study aimed to evaluate the performance and practicability of manual Mycobacteria Growth Indicator Tube [MGIT] in performing indirect susceptibility testing of M. tuberculosis. The reliability of manual MGIT for testing susceptibilities of 318 M. tuberculosis isolates to streptomycin [SM], isoniazid [INH], rifampin [RIF] and ethambutol [EMB] was evaluated in comparison with conventional indirect method of proportion [MOP]. MGIT detected overall drug resistance of; 50%, 59.4%, 40.3% and 37.1% as well as resistances among new cases of; 22%, 26.7%, 15.5% and 15.4% and resistances among treated cases of; 28%, 32.7%, 24.8% and 21.7% for SM, INH, RIF and EMB, respectively. Multi-drug resistant tuberculosis [MDR-TB] among new cases was 3.3% and that among treated cases was 12.4%. MGIT showed very good agreement with MOP susceptibility testing results [Kappa ranged from 0.7 to 0.82]. For MDR-TB detection there is 100% agreement between the two methods. The turnaround times [TAT] "from specimen processing to reporting of the antimicrobial susceptibility testing [AST] results" ranged between 10 and 30 days [mean=17.4] by the indirect MGIT method and 31 and 73 days [mean=48.9] by the indirect MOP. Manual MGIT appears to be a reliable, rapid and convenient method for performing indirect DSTs of M. tuberculosis in low-resource settings