ABSTRACT
Objective To investigate correlation between the results of drug susceptibility and the extent of drug-resistances in Mycobacterium tuberculosis clinical isolates. Methods Liquid culture and MTT test were used. Twelve anti-TB drug MICs and drug susceptibility testing of the 163 MTB strains from random clinical isolates were detected, which including RFP, INH, SM, EBM, OFLX, LVFX, MOX, AMK,CPM, PTA, CLA and PAIN. Results There are 67% (42/62) Mycobacterium tuberculosis strains resistant to SM, 63% (51/81) Mycobacterium tuberculosis strains resistant to INH, 77% (50/65) Mycobacterium tuberculosis strains resistant to RFP, 41% ( 15/37 ) Mycobacterium tuberculosis strains resistant to AMK,41% (12/29) Mycobacterium tuberculosis strains resistant to CPM, 20% (12/60) Mycobacterium tuberculosis strains resistant to EMB and 43% (25/58) Mycobacterium tuberculosis strains resistant to OFLX which MICs were equal to or more than 16 μg/ml, 8 μg/ml, 8 μg/ml, 16 μg/ml and 4 μg/ml, 4 μg/ml and 8 μg/ml,respectively. There were significant differences in the MICs of OFLX, LVFX and MOX in OFLX resistant strains (2-128, 1-32 and 0.0625-1 μg/ml, respectively) by ANOVA ( F = 16.874, P ＜ 0.001 ). The MICs of SM, INH, RFP, EMB, OFLX, AMK and CPM in isolates resistant to six or seven drugs (0.5-128,2-64,0.25-128,1-32,1-64,0.5-128 and 1-128 μg/ml,respectively) were higher than those (0.25-128,0.0625-64,0.25-32,0.25-2,0.125-2,0.5-4 and 1-4 μg/ml,respectively) in isolates resistant to one or two drugs (F=20.066, 40.499, 47. 197, 70.373, 91.432, 41.840 and 21.547, respectively, P ＜0.05). The MICs of SM, INH, RFP and EMB in isolates resistant to four drugs (1-128,2-64,0.25-128 and 1-32 μg/ml,respectively ) were higher than those ( 0.25-128,0.0625-64, 0.25-64 and 0.25-2 μg/ml,respectively) in isolates resistant to one or two drugs (F = 26.242, 23.563, 31.541 and 64.469,respectively, P ＜0.05).The MICs of RFP in MDR isolates (2-64 μg/ml) were higher than those (0. 25 μg/ml) in other resistant isolate except M DR isolates (F = 5.613, P <0.05). Conclusions The study shows that there are associations between the results of routine drug susceptibility testing and the resistant extent of anti-TB drugs. This could help doctors select more effective anti-TB regimen for TB patients according to the correlations.