Abstract：Objective To analyze the mechanism of discordance between molecular drug susceptibility testing (Xpert MTB/RIF assay) and phenotypic drug susceptibility testing (Bactec MGIT 960 culture system) of rifampicin-resistant Mycobacterium tuberculosis. Methods We collected 46 specimens (including 39 specimens that were rifampicin-resistant by the Xpert MTB/RIF assay but rifampicin-sensitive by MGIT 960 culture and 7 specimens that were rifampicin-sensitive by the Xpert MTB/RIF assay but rifampicin-resistant by MGIT 960 culture) from 8,274 patients with Xpert MTB/RIF detection in the First Affiliated Hospital of Changsha Medical University from October 2015 to April 2018, then tried to get the isolates form the 46 specimens and figured out the rifampicin resistance determining region (RRDR) with rpoB gene detection. The minimum inhibitory concentration (MIC) in the recovered isolates was simultaneously determined, and the degree of resistance for different mutation isolates was observed. Results Among the 46 specimens, 2 isolates were failed and another 2 were lost. The remaining 42 isolates were sequenced, and there were 5 isolates without rpoB mutation and 37 isolates had diverse gene variations. The main mutation loci were concentrated in 511, 516, 526, 531 and 533 sites. The leading locus was 526, and there were 4 types of mutation, including His526Asn, His526Leu, His526Gly and His526Cys. The types of mutation in other loci were Leu511Pro, Asp516Tyr and Leu533Pro. As for the isolates with mutation located in 511, 516, 526 and 533 sites, the MIC of one isolate with His526Leu mutation was 32 μg/ml, but the others displayed low-level susceptibility or resistance. As for the isolates with mutation located in 531, Ser531Trp and Ser531Leu mutation displayed high-level resistance. Conclusions The Results based on rpoB sequence and MIC measurement show that the specific rpoB gene mutation may lead to the changes of rifampin resistance in Mycobacterium tuberculosis. There are discordant Results between the Xpert MTB/RIF assay and Bactec MGIT 960 culture system for detection of rifampin-resistant Mycobacterium tuberculosis.
李敏, 李大兴, 杨奇, 吴金娣, 王洪瑛. 结核分枝杆菌利福平分子药敏结果与其表型药敏差异的研究[J]. 实用预防医学, 2019, 26(1): 46-50.
LI Min, LI Da-xing, YANG Qi, WU Jin-di, WANG Hong-ying. Discordance across molecular and phenotypic methodsfor drug susceptibility testing of rifampicin-resistant Mycobacterium tuberculosis. , 2019, 26(1): 46-50.
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2019, Vol. 26 
