AUTHOR=Li Ma-chao , Chen Rong , Lin Shi-qiang , Lu Yao , Liu Hai-can , Li Gui-lian , Liu Zhi-guang , Zhao Xiu-qin , Zhao Li-li , Wan Kang-Lin 

TITLE=Detecting Ethambutol Resistance in Mycobacterium tuberculosis Isolates in China: A Comparison Between Phenotypic Drug Susceptibility Testing Methods and DNA Sequencing of embAB

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.00781

DOI=10.3389/fmicb.2020.00781

ISSN=1664-302X

ABSTRACT=<p>With the increasing incidence of drug-resistant tuberculosis (DR-TB), determining a rapid and accurate drug susceptibility testing (DST) method to identify ethambutol (EMB) resistance in <italic>Mycobacterium tuberculosis</italic> has become essential for patient management in China. Herein, we evaluated the correlation between three phenotypic DST methods, namely, proportion method (PM), MGIT 960 system, and microplate alamar Blue assay (MABA), and DNA sequencing of <italic>embAB</italic> in 118 <italic>M. tuberculosis</italic> isolates from China. When the results of the phenotypic DST methods were compared with those of DNA sequencing, the overall agreement and kappa values of the PM, MGIT 960 system, and MABA were 81.4% and 0.61, 77.1% and 0.55, and 84.7% and 0.67, respectively. The agreement for EMB resistance between MABA and PM was significantly higher than that between the MGIT 960 system and PM (<italic>P</italic> = 0.02). Moreover, among the isolates with detectable <italic>embAB</italic> mutations, 97.2% (70/72 isolates) harbored mutations in <italic>embB</italic>. The analysis of <italic>embB</italic> mutations predicted EMB resistance with 81.3% sensitivity, 86.8% specificity, and 83.1% accuracy. Thus, MABA may be a better phenotypic DST method for detecting EMB resistance. DNA sequencing of <italic>embB</italic> may be useful for the early identification of EMB resistance and the consequent optimization of the treatment regimen.</p>