Objective To understand the drug resistance of Mycobacterium tuberculosis in three tuberculosis-specialized hospitals in Gansu and Shaanxi provinces in northwestern China, compare and analyze the resistance patterns and epidemiological characteristics of M. tuberculosis in Lanzhou, Gansu province, and Xi'an, Shaanxi province, and provide reference for the rational use of anti-tuberculosis drugs in clinical practice.

Methods A retrospective study was conducted in cultured M. tuberculosis positive patients admitted to three tuberculosis-specialized hospitals in 2020 and in 2023, i.e. Lanzhou Pulmonary Hospital, Xi'an Chest Hospital, and Shaanxi Provincial Tuberculosis Prevention and Control Hospital, In total, 493 tuberculosis cases were from Lanzhou and 704 tuberculosis cases were from Xi'an. The drug susceptibility testing of M. tuberculosis isolates was performed by using the microplate method. Date were analyzed with software SPSS 26.0, and P <0.05 was defined as statistically significant.

Results The overall drug resistance rate of M. tuberculosis strains in Lanzhou was 33.47% (165/493), significantly higher than that in Xi'an (24.15%, 170/704) (χ²=12.499, P<0.001). Both the multi-drug resistance (MDR) and pre-extensive drug resistance (pre-XDR) rates in Lanzhou were also significantly higher than those in Xi'an (χ²=9.709, 5.283, P=0.002, 0.022). Among them, the resistance rates to isoniazid, rifampicin, pasiniazide, levofloxacin (LFX), moxifloxacin (MFX), ethambutol (EMB), clofazimine (CFZ) and kanamycin in tuberculosis patients were significantly higher in Lanzhou than in Xi 'an (all P<0.05). Compared with 2020, the MDR rate decreased significantly in 2023 (χ²=4.272, P=0.039), whereas the pre-XDR rate increased significantly in Lanzhou (χ²=4.404, P=0.036). In Xi'an, the MDR rate decreased significantly in 2023 (χ²=4.757, P=0.029). In Lanzhou, the resistance rates to LFX, MFX, EMB, CFZ increased significantly in 2023 compared with 2020 (all P<0.05).

Conclusion The drug resistance of M. tuberculosis remains severe in Lanzhou, especially the pre-XDR and the increased resistance to fluoroquinolone. It is necessary to strengthen the management of fluoroquinolone use, improve the adherence to standardized treatment and health service management for tuberculosis patients to reduce the emergence of drug-resistant strains. Meanwhile, the timely detection of drug-resistant cases should be conducted to curb the transmission and of drug-resistant tuberculosis.