Performance of the microscopic observation drug susceptibility assay in pyrazinamide susceptibility testing for Mycobacterium tuberculosis  

作　　者：HUANG Zi-kun LUO Qing JIANG Bi-xia LI Wei-ting XU Xiao-meng XIONG Guo-liang and LI Jun-ming 

机构地区：[1]Department of Clinical Laboratory, First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi 330006, China [2]Department of Clinical Laboratory, Chest Hospital of Jiangxi Province, Nanchang, Jiangxi 330006, China

出　　处：《Chinese Medical Journal》2013年第22期4334-4339,共6页中华医学杂志（英文版）

基　　金：This study was supported by grants from the National Natural Science Foundation of China （No. 81060001 ） and the Foundation of Scientific ＆ Technical Research Project of Jiangxi Province （No. 2009BSB11219）.

摘　　要：Background Drug susceptibility assay is very important in tuberculosis therapy. Pyrazinamide is a first line antituberculosis drug and diagnosis of its resistance in Mycobacterium tuberculosis （M. tuberculosis） is difficult and time consuming by conventional methods. In this study, we aimed to evaluate the performance of the microscopic observation drug susceptibility （MODS） assay in the detection of pyrazinamide resistance in M. tuberculosis relative to the conventional Wayne assay and Lowenstein-Jensen （L J） proportion method. Methods M. tuberculosis clinical isolates （n=132） were tested by the MODS and the Wayne assay： the results were compared with those obtained by the LJ proportion method. Mutations in the gene were identified by direct sequencing of the pncA genes of all isolates in which pyrazinamide resistance was detected by any of the three methods. Results Compared to the LJ results, the sensitivity and specificity of the MODS assay were 97.8% and 96.5% respectively; the sensitivity and specificity of the Wayne assay were 87.0% and 97.7% respectively. Mutations in the pncA gene were found in 41 of 46 strains that were pyrazinamide resistant （3 tests）, in 1 of the 4 strains （LJ only）, in 42 of 48 strains （at least I test）, but no mutations in 1 strain sensitive according to the MODS assay only. The MODS assay, Wayne assay and LJ proportion method provided results in a median time of 6, 7 and 26 days respectively. Conclusions MODS assay offers a rapid, simple and reliable method for the detection of pyrazinamide resistance in M. tuberculosis and is an optimal alternative method in resource limited countries.Background Drug susceptibility assay is very important in tuberculosis therapy. Pyrazinamide is a first line antituberculosis drug and diagnosis of its resistance in Mycobacterium tuberculosis （M. tuberculosis） is difficult and time consuming by conventional methods. In this study, we aimed to evaluate the performance of the microscopic observation drug susceptibility （MODS） assay in the detection of pyrazinamide resistance in M. tuberculosis relative to the conventional Wayne assay and Lowenstein-Jensen （L J） proportion method. Methods M. tuberculosis clinical isolates （n=132） were tested by the MODS and the Wayne assay： the results were compared with those obtained by the LJ proportion method. Mutations in the gene were identified by direct sequencing of the pncA genes of all isolates in which pyrazinamide resistance was detected by any of the three methods. Results Compared to the LJ results, the sensitivity and specificity of the MODS assay were 97.8% and 96.5% respectively; the sensitivity and specificity of the Wayne assay were 87.0% and 97.7% respectively. Mutations in the pncA gene were found in 41 of 46 strains that were pyrazinamide resistant （3 tests）, in 1 of the 4 strains （LJ only）, in 42 of 48 strains （at least I test）, but no mutations in 1 strain sensitive according to the MODS assay only. The MODS assay, Wayne assay and LJ proportion method provided results in a median time of 6, 7 and 26 days respectively. Conclusions MODS assay offers a rapid, simple and reliable method for the detection of pyrazinamide resistance in M. tuberculosis and is an optimal alternative method in resource limited countries.

关 键 词：microscopic observation drug susceptibility Mycobacterium tuberculosis susceptibility test PYRAZINAMIDE 

分 类 号：R96[医药卫生—药理学]