Characterization of Fluoroquinolone-Resistant and Multidrug-Resistant Mycobacterium tuberculosis Isolates Using Whole-Genome Sequencing in Tianjin, China

Objective: Tuberculosis (TB) caused by Mycobacterium tuberculosis remains a global concern. This study aimed to determine the molecular characteristics of fluoroquinolone-resistant and multidrug-resistant M. tuberculosis strains using whole-genome sequencing to predict drug resistance in M. tuberculosis in Tianjin, China, which has not been established previously. Methods: Twenty-one fluoroquinolone-resistant and multidrug-resistant M. tuberculosis strains were isolated from sputum samples. Phenotypic drug resistance against 12 anti-tuberculosis drugs was determined using drug susceptibility testing. Whole-genome sequencing was performed to predict drug resistance in M. tuberculosis based on genome regions associated with drug resistance. The sensitivity of whole-genome sequencing for predicting drug resistance was calculated based on phenotypic drug susceptibility testing information. Results: Among the 21 isolates, mutations in 15 genome regions associated with drug resistance, including rpoB for rifampicin; katG and inhA promoter for isoniazid; gyrA and gyrB for ofloxacin and moxifloxacin; rpsL for streptomycin; rrs for streptomycin, amikacin, kanamycin and capreomycin; pncA and panD for pyrazinamide; embB, embC-embA, aftA , and ubiA for ethambutol; ethA for protionamide; and folC for para-aminosalicylic acid, were detected. Compared with traditional drug susceptibility testing results, the sensitivities for whole-genome sequencing of rifampin, isoniazid, ofloxacin, moxifloxacin, streptomycin, ethambutol, pyrazinamide, kanamycin, and amikacin resistance were 100%, 90.48%, 95.24%, 92.86%, 95.27%, 85.71%, 66.67%, 50%, and 50%, respectively. The sensitivities for whole-genome sequencing of capreomycin, protionamide, and para-aminosalicylic acid were not calculated because only one isolate showed phenotypic drug resistance. Mutations determined in drug susceptibility-associated genes can explain phenotypic drug resistance in most isolates. Notably, these mutations were absent in certain drug-resistant isolates, indicating other drug resistance mechanisms. Conclusion: Whole-genome sequencing represents an effective diagnostic tool for fluoroquinolone-resistant and multidrug-resistant TB though it has some obstacles. Whole-genome sequencing should be used to predict drug resistance prior to performing traditional phenotypic drug susceptibility testing in Tianjin, China. Keywords: Mycobacterium tuberculosis , tuberculosis, fluoroquinolone, mutation, drug resistance, whole-genome sequencing