2.4. Quantitative real-time PCR

DNA was extracted by Glass bead method (Method 2.2), 2 μL DNA was added into 18 μL amplification mixture (Mycobacterium nucleic acid detection kit (PCR - fluorescent probe method) (CapitalBio Technology, Beijing, China)), in a final volume of 20 μL. And PCR reaction was performed by ABI 7500 PCR instrument (Applied Biosystems Inc., United States). The reaction program was: 37°C, 300 s; 94°C, 180 s; 94°C, 15 s, 60°C, 30s for 40 cycles; 50°C, 10s. The fluorescence collection points were selected at 60°C, 30s. The target gene was IS6110.