Kumar Vipin, Bala Manju, Kanga Anil, Gautam Neha
Senior Resident, Microbiology, Dr. YS Parmar Govt Medical College, Nahan, Himachal Pradesh.
Associate Professsor, Microbiology, Dr. YS Parmar Govt Medical College, Nahan, Himachal Pradesh.
J Assoc Physicians India. 2020 Nov;68(11):33-36.
India has the highest number of TB (27%) and MDR/RR-TB (24%) cases among the notified TB patients. Xpert MTB/ RIF assay is a fully automated cartridge-based real-time PCR to detect MTB and resistance to rifampicin within two hours using three specific primers and five unique molecular probes to target the rpoB gene. This study was done to detect RR-TB cases and frequency of missing probes, which target mutations in rpoB gene, in the different groups of study population in Sirmaur district of Himachal Pradesh.
All, pulmonary and extrapulmonary specimens, were processed for AFB microscopy and Xpert MTB/RIF assay to diagnose TB and RR-TB.
Xpert detected MTBC in 721 patients. Using AFB microscopy, only 284 samples were positive. Of these MTB positive patients, 671 had pulmonary TB and 50 were EPTB cases. Resistance to RIF was detected in 31 (4.29%) cases of which resistance in presumptive tuberculosis group and presumptive drug resistant tuberculosis was 1.51% and 9.30% respectively. Twentyeight (4.17%) PTB cases and three (6%) EP-TB cases were resistant to RIF. The frequency of probe E was highest (77.41%) and mutation combination of probes C and D and E and D was 3.22%.
Drug resistance in the MTBC is mainly conferred through point mutations in specific gene targets in the bacterial genome. Molecular assays like Genexpert gives rapid diagnosis and Rifampicin resistance. This study helps to provide baseline data of mutations with in the 81 bp of rpoB gene and stresses the need to further evaluate the mutation patterns in this part of the country.
在已通报的结核病患者中，印度的结核病病例数（27%）和耐多药/利福平耐药结核病（MDR/RR-TB）病例数（24%）最多。Xpert MTB/RIF检测是一种基于试剂盒的全自动实时PCR技术，使用三种特异性引物和五种独特的分子探针靶向rpoB基因，可在两小时内检测结核分枝杆菌（MTB）和对利福平的耐药性。本研究旨在检测喜马偕尔邦锡尔默尔地区不同研究人群中RR-TB病例以及靶向rpoB基因突变的缺失探针频率。
所有肺标本和肺外标本均进行抗酸杆菌（AFB）显微镜检查和Xpert MTB/RIF检测，以诊断结核病和RR-TB。
Xpert在721例患者中检测到结核分枝杆菌复合群（MTBC）。使用AFB显微镜检查，仅284份样本呈阳性。在这些MTB阳性患者中，671例为肺结核，50例为肺外结核病例。在31例（4.29%）病例中检测到对利福平耐药，其中疑似结核病组和疑似耐多药结核病组的耐药率分别为1.51%和9.30%。28例（4.17%）肺结核病例和3例（6%）肺外结核病例对利福平耐药。探针E的频率最高（77.41%），探针C与D以及探针E与D的突变组合为3.22%。
MTBC中的耐药性主要通过细菌基因组中特定基因靶点的点突变产生。像GeneXpert这样的分子检测可实现快速诊断和利福平耐药性检测。本研究有助于提供rpoB基因81bp内突变的基线数据，并强调有必要进一步评估该国这一地区的突变模式。
