Department of Clinical Laboratory, First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi 330006, China.
Chin Med J (Engl). 2013 Nov;126(22):4334-9.
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 (LJ) proportion method.
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.
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 1 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.
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.
药敏试验在结核病治疗中非常重要。吡嗪酰胺是一种一线抗结核药物，传统方法诊断其对结核分枝杆菌（M. tuberculosis）的耐药性既困难又耗时。本研究旨在评估相对于传统的 Wayne 法和 Lowenstein-Jensen（LJ）比例法，微量观察药物敏感性（MODS）法检测结核分枝杆菌吡嗪酰胺耐药性的性能。
对 132 株结核分枝杆菌临床分离株进行 MODS 和 Wayne 法检测：将结果与 LJ 比例法的结果进行比较。通过直接测序所有三种方法均检测到吡嗪酰胺耐药的分离株的 pncA 基因，鉴定基因中的突变。
与 LJ 结果相比，MODS 检测的敏感性和特异性分别为 97.8%和 96.5%；Wayne 检测的敏感性和特异性分别为 87.0%和 97.7%。在 46 株吡嗪酰胺耐药（3 种检测方法）的菌株中发现 pncA 基因突变，在 4 株（仅 LJ）、48 株（至少 1 种检测方法）菌株中发现 pncA 基因突变，但在仅根据 MODS 检测方法敏感的 1 株菌株中未发现突变。MODS 检测、Wayne 检测和 LJ 比例法的中位检测时间分别为 6、7 和 26 天。
MODS 检测法为检测结核分枝杆菌吡嗪酰胺耐药性提供了一种快速、简单、可靠的方法，是资源有限国家的最佳替代方法。
