Broth dilution method for the resistance of Mycobacterium tuberculosis isolates to protionamide / 中国人兽共患病学报

ABSTRACT

We compared the MGIT 960 method,the reference,and the broth microdilution method for detecting the susceptibility of Mycobacterium tuberculosis isolates to protionamide (PTO).We performed drug susceptibility testing for 248 M.tuberculosis clinical isolates to PTO using MGIT 960 and broth microdilution method.In addition,a total of 117 isolates were randomly selected for further evaluation of the consistency of the minimal inhibitory concentrations determined by these two methods,and eleven concentrations of PTO had been involved accordingly (0.062 5,0.125,0.25,0.5,1,2,4,8,16,32,64 μg/mL).The MGIT method showed an average detection time of 10.1 days,while the detection period of broth microdilution method was 8 days,and the difference was statistically significant (P＜0.001).In addition,the rate of the sensitivity,specificity and concordance between these two methods was 96.5％ (55/57),93.2％ (178/191),and 94.0％ (233/248),respectively.The Kappa value was 0.84.Comparison of the MIC values detected by different methods revealed that the overall concordance rate was 81.2％ (95/117).For the isolates harboring low MIC values (MIC＜8.0 μg/mL),the concordance rate was 86.3％ (82/95),while that of the isolates with high MIC values was only 59.1％ (13/22).In conclusion,our data demonstrate that the broth microdilution method showed excellent concordance with MGIT method for detecting the resistance rate of M.tuberculosis isolates to PTO,indicating that the broth microdilution method with available performance,short turn-around time and convenient manual operation was suitable for rapid detection of M.tuberculosis to PTO.