Abstract: Objective  To investigate the drug resistance and the cross resistance of Mycobacterium tuberculosis isolated from clinical samples to streptomycin (S), kanamycin (Km), amikacin (Am) and capreomycin (Cm) and to provide scientific evidences for clinical treatment of drug resistance tuberculosis. Methods  A retrospective study was adopted to analyze the results of drug susceptibility testing(DST) with absolute concentration method of 4247 isolates from patients with tuberculosis in Beijing Chest Hospital from Jan. 2004 to Dec. 2010. Mathed Chi-square test and partition of chi-square were applied for the overall drug resistant rate analysis, while chi-square test was applied to compare the cross resistance to 4 injectable antituberculous drugs. Results  The drug resistant rates to the four drugs were 45.11%(S, 1916/4247), 17.93%(Km, 718/4005), 19.02%(Am,792/4164) and 9.44%(Cm, 401/4247) among 4247 resistant isolates respectively. The differences were statistically significant by matched χ² test and partitions of χ² method. The values of χ² were 1349.34 (Cm/S), 281.54 (Cm/Am) and 193.16 (Cm/Km) (P<0.007 14) respectively. For the drug resistant rates of S/Am and S/Km, the values of χ² were 821.10 (S/Am) and 869.28 (S/Km) (P<0.007 14) respectively. The value of χ² was 13.98 (Am/Km) (P<0.007 14). The drug resistant rates sequencing from up to down were S, Am, Km and Cm. The drug resistant rates to S among the other 3 drug-resistance isolates were 82.59%(Km resistant isolates, 593/718), 77.78%(Am resistant isolates, 616/792) and 76.81%(Cm resistant isolates, 308/401) respectively. The values of χ² were 502.959, 453.911 and 626.654 (P<0.05). The drug resistant rates to Km among the other 3 drug-resistance isolates were 33.13%(S resistant isolates, 593/1790), 83.31%(Am resistant isolates, 634/761) and 67.89%(Cm resistant isolates, 260/383) respectively. The values of χ² were 502.959, 12.079 and 100.536 (P<0.05). The drug resistant rates to Am among the other 3 drug-resistance isolates were 32.78%(S resistant isolates, 616/1879), 89.55%(Km resistant isolates, 634/708) and 77.95%(Cm resistant isolates, 304/390) respectively. The values of χ² were 453.911, 12.079 and 163.761 (P<0.05). The drug resistant rates to Cm among the other three drug resistance isolates were 16.08%(S resistant isolates, 308/1916), 36.21%(Km resistant isolates, 260/718) and 38.38%(Am resistant isolates, 304/792) respectively. The values of χ² were 626.654, 100.536 and 163.761(P<0.05). Conclusion  The drug resistant rates sequencing from up to down of four injectable antituberculous drugs are streptomycin, amikacin, kanamycin and capreomycin. There are cross resistances among these four drugs with different levels. Streptomycin is unidirectional resistant to the other three drugs. Kanamycin and amikacin are almost full cross-resistant. Capreomycin is the candidate drug when the other three drugs are resistant.

Key words: Mycobacterium tuberculosis, Streptomycin, Kanamycin, Amikacin, Capreomycin sulfate, Drug resistance, bacterial