传染病信息

目的 探究结核分枝杆菌/利福平耐药实时荧光定量核酸扩增检测（geneXpert Mycobacterium tuberculosis/Rifampin, Xpert MTB/RIF）技术对痰涂片结核分枝杆菌（Mycobacterium tuberculosis, MTB）感染及利福平耐药的诊断效能，并分析耐药基因突变特征。方法 选择2020年1月至2022年1月秦皇岛市第三医院收治的177例疑似结核病患者作为研究对象。按年龄五分位数法将患者分为5组。以临床诊断为金标准确诊MTB感染情况，比较不同性别、年龄、痰涂片结果及药物敏感性（药敏）结果人群的Xpert MTB/RIF检测阳性率；分别以临床诊断、药敏试验绝对浓度法为金标准，通过受试者工作特征（receiver operating characteristic, ROC）曲线评估Xpert MTB/RIF技术对MTB感染及利福平耐药性的诊断效能；分析MTB对利福平耐药相关rpoB基因的突变特征；分别比较不同遗传背景及不同利福平耐药程度MTB的rpoB基因突变率及突变特征。结果 23～56岁患者MTB感染阳性率显著高于其他高年龄段患者（P <0.05）;Xpert MTB/RIF技术检测结果与痰涂片及药敏结果比较差异具有统计学意义（P <0.05）。Xpert MTB/RIF技术诊断MTB感染的ROC曲线下面积为0.876(95%CI:0.812～0.939)，灵敏度为94.62%(88/93)，特异度为84.52%(71/84)，阳性预测值为87.13%(88/101)，阴性预测值为93.42%(71/76)，准确度为89.83%(159/177)；诊断MTB对利福平耐药的ROC曲线下面积为0.812(95%CI:0.753～0.882)，灵敏度为74.19%(23/31)，特异度为91.94%(57/62)，阳性预测值为82.14%(23/28)，阴性预测值为87.69%(57/65)，准确度为86.02%(80/93)。Xpert MTB/RIF技术检测的28株rpoB基因突变菌株中，双位点突变占3.23%(1/28)，其余均为单一位点突变[96.43%(27/28)]，以531位点（TCG→TTG）突变类型为主[29.03%(9/28)]；非北京基因型与北京基因型MTB的rpo B基因突变率及突变类型差异均无统计学意义（P均> 0.05）；低浓度耐药株、高浓度耐药株间的rpo B基因突变率及突变类型为526(CAC→TAC)、531(TCG→TTG)的检出率差异具有统计学意义（P <0.05）。结论 Xpert MTB/RIF技术对痰涂片MTB感染及利福平耐药性有较高的诊断价值，利福平耐药rpo B基因以531(TCG→TTG)突变类型为主。

Objective To explore the diagnostic efficacy of real-time fluorescence quantitative nucleic acid amplification assay(Xpert MTB/RIF) for Mycobacterium tuberculosis(MTB) infection and rifampicin resistance in sputum smear-positive specimens, and to analyze the characteristics of drug-resistant gene mutations. Methods A total of 177 suspected tuberculosis patients admitted to the Third Hospital of Qinhuangdao from January 2020 to January 2022 were enrolled. The clinical diagnosis was regarded as the gold standard for confirming MTB infection. The positive rates of Xpert MTB/RIF were compared across different genders, age groups, sputum smear results and drug sensitivity test outcomes. The diagnostic efficiency of Xpert MTB/RIF for MTB infection and rifampicin resistance was evaluated by receiver operating characteristic(ROC) curve, with clinical diagnosis and absolute concentration method of drug susceptibility test as the gold standard. Additionally, the mutation characteristics of rpoB gene associated with rifampicin resistance in MTB were analyzed. The rpoB gene mutation rate and mutation characteristics of MTB with different genetic background and different degree of rifampicin resistance were further compared. Results Patients were divided into 5 groups according to quintiles of age. The positive rate of MTB infection in patients aged 23-56 years was significantly higher than that in other older age groups(P <0.05). There was a significant difference between the results of Xpert MTB/RIF and the results of sputum smear and drug sensitivity(P <0.05). The area under the ROC curve of Xpert MTB/RIF for the diagnosis of MTB infection was 0.876(95%CI: 0.812-0.939), specifically, the sensitivity was 94.62%(88/93), the specificity was 84.52%(71/84), the positive predictive value was 87.13%(88/101), the negative predictive value was 93.42%(71/76), and the accuracy was 89.83%(159/177). The area under the ROC curve for the diagnosis of rifampicin resistance of MTB was 0.812(95%CI:0.753-0.882), the sensitivity was 74.19%(23/31), the specificity was 91.94%(57/62), the positive predictive value was 82.14%(23/28), the negative predictive value was 87.69%(57/65), and the accuracy was 86.02%(80/93). Among the 28 strains with rpoB gene mutations detected by Xpert MTB/RIF, the double-site mutations accounted for 3.23%(1/28), while the remaining were single-site mutations [96.43%(27/28)], and the predominant mutation type was at 531 site(TCG→TTG) [29.03%(9/28)]. There was no significant difference in rpoB gene mutation rate or mutation type between non-Beijing genotype MTB and Beijing genotype MTB(all P >0.05). By contrast, there were significant differences in the mutation rate of rpoB gene and the detection rate of mutation type 526(CAC→TAC) and 531(TCG→TTG) between the low concentration and high concentration resistant strains(P <0.05). Conclusions Xpert MTB/RIF technique has high applicationvalue for MTB infection diagnosis in sputum smears and rifampicin resistance. Five hundred and thirty-one(TCG→TTG) mutation is the predominant type of rifampin resistant rpoB gene.