RESUMEN
@#Abstract: Objective To collect extensively drug-resistant tuberculosis (XDR-TB) Mycobacterium tuberculosis strains isolated from Xi'an City between 2019 and 2020, and analyze the drug resistance patterns of XDR-TB strains to second-line anti-tuberculosis drugs and the occurrence of new defined extensively drug-resistant tuberculosis in Xi'an, in order to provide evidence for guiding clinical drug use of multidrug-resistant tuberculosis (MDR-TB) patients. Methods A total of 3 088 strains of Mycobacterium tuberculosis that underwent phenotypic drug susceptibility testing at Xi'an Chest Hospital from January 2019 to December 2020 were retrospectively selected to analyze the resistance of anti-tuberculosis drug. Among the stored MDR-TB strains, 114 strains of preserved multidrug-resistant Mycobacterium tuberculosis were randomly selected for bedaquiline and linezolid susceptibility testing. Combined with the results of previous second-line drug susceptibility testing, the incidence of newly defined extensive drug resistance was analyzed. Results Among the 3 088 Mycobacterium tuberculosis strains analyzed, 411 strains (14.3%) showed resistance to isoniazid, 347 strains (11.2%) showed resistance to rifampicin, 142 strains (4.6%) showed resistance to ethambutol, 550 strains (17.8%) showed resistance to streptomycin, and 237 strains (7.6%) exhibited multidrug resistance. Of 237 MDR-TB strains, the resistance rates of ethambutol, moxifloxacin, rifampicin, sodium para-aminosalicylate, prothioconazole, capreomycin, amikacin, and clofazimine were 44.3%, 26.6%, 33.3%, 24.1%, 5.1%, 4.2%, 3.0%, and 2.5%, respectively. Among the randomly selected 114 MDR-TB strains, none showed resistance to bedaquiline, three showed resistance to linezolid, and one strain met the new definition for extensively drug-resistant tuberculosis. Conclusion In Xi'an City, high rates of resistance among MDR-TB strains are observed for ethambutol, quinolone and sodium para-aminosalicylate, and the drug susceptibility tests should be obtained as much as possible when using these drugs. The incidence of new definition extensively drug-resistant tuberculosis is low, and bedaquiline and linezolid remain effective drugs for the treatment of multidrug-resistant tuberculosis even without drug susceptibility testing results.