Abstract: Objective  To observe the levels of the resistance and cross-resistance to streptomycin (Sm), kanamycin (Km), amikacin (Am), capreomycin (Cm) in Mycobacterium tuberculosis (Mtb) clinical strains by drug susceptibility test (DST).  Methods  The MICs of Sm, Km, Am, and Cm in 117 Mtb clinical strains were detected by microplate Alamar blue assay (MABA). The critical concentration of Sm, Km, Am, and Cm on Mtb were 2, 4, 1 and 2.5 μg/ml, respectively. When the MICs of Sm/Km/Am on Mtb were greater than critical concentration and ≤16 μg/ml, or 32-64 μg/ml, or >64 μg/ml, the drug resistances were defined as low level, moderate level, and high level, respectively. But that for Cm on Mtb was greater than critical concentration and ≤20 μg/ml, or 40-80 μg/ml, or >80 μg/ml.  Results  Of 117 Mtb clinical isolates, 83 were Sm-resistant, in which 63 isolates（75.9%）were high resitance, 18 isolates （21.7%） were low resistance, 2 isolates （2.4%） were moderate resis-tance. 78.3% of 23 Km-resistant strains and 94.7% of 19 Am-resistant strains were high-level resistance (MIC≥128 μg/ml), other isolates were low-level resistant to Am/Km, no moderate-level resistant isolates were observed. The MICs of 14 Cm-resistant isolates were 5-20 μg/ml, and there were not high level of Cm-resistant isolates. Of 83 Sm-resistant isolates, 27.7% (23/83) and 22.9% (19/83) were resistant to Km and Am respectively, 71.1% (59/83) were sensitive to both Km and Am. 78.3% (18/23) of Km-resistant isolates and 94.7% (18/19) of Am-resistant isolates were highly resistant to both Km and Am, which had no significant difference （χ²=1.157,P>0.05）. Five strains were low resistance to Km, but sensitive to Am. 68.4%（13/19） of Am-resistant isolates and 92.9% (13/14) of Cm-resistant isolates were resistant to both Am and Cm.  Conclusion  The majority of the Sm/Km/Am-resistant clinical isolates were high resistance, and the majority of the Cm-resistant clinical isolates were low resistance. Most of highly Sm-resistant isolates were susceptible to Km/Am. The highly Am/Km-resis-tant isolates showed cross resistance each other. A small proportion of lowly Km-resistant isolates were sensitive to Am. Most of highly Am-resistant isolates were low resistance to Cm. Almost all of Cm-resistant isolates were high resistant to Am.

Key words: Mycobacterium tuberculosis, Antitubercular agents, Drug resistance, bacterial