Abstract:

Objective To compare the performance of MGIT 960 system,pyrazinamidase（PZase） activity assay and pncA gene sequencing for the determination of Mycobacterium tuberculosis drug resistance to pyrazinamide （PZA）. Methods The drug resistance to PZA of 207 Mycobacterium tuberculosis isolates from Shanghai Municipal Center for Disease Control and Prevention in 2014 were determined by the 3 methods. Results There were 38 isolates with inconsistent results by the 3 methods. After repeated experiments,10 of 13 isolates reported as PZA being resistant by MGIT 960 system proved susceptible. When the results were consistent in 2 methods or more than 2 methods as reference results,the sensitivities of MGIT 960 system,PZase activity assay and pncA gene sequencing were 94.8%,100.0% and 94.8%,respectively. The specificities of MGIT 960 system,PZase activity assay and pncA gene sequencing were 93.3%,83.9% and 98.0%,respectively. Compared with the reference results,the Kappa values of MGIT 960 system,PZase activity assay and pncA gene sequencing were 0.85,0.74 and 0.93,respectively. Conclusions The performance of MGIT 960 system and pncA gene sequencing shows consistency with the reference results. There exists false positive results for PZA drug resistance determination by MGIT 960 system. Mycobacterium tuberculosis isolates report as PZA being resistant by MGIT 960 system,which should be determined by pncA gene sequencing. If the 2 methods have inconsistent results,repeated experiments should be performed for improving the accuracy of PZA drug resistance determination.

Key words: Mycobacterium tuberculosis, Pyrazinamide, Drug resistance