Improvement of Mycobacterium tuberculosis detection in sputum using DNA extracted by sonication.

Tuberculosis (TB) is one of the infectious diseases with high mortality in the world. DNA amplification techniques have been used to overcome barriers to the diagnosis of this disease. However, the success of these methodologies is highly dependent on the DNA obtained from the sample. This study was carried out to verify whether the DNA extracted by sonication (in house method) could yield suitable DNA for amplification by real-time PCR (qPCR). Sixty sputum samples were submitted to DNA extraction using sonication compared to a commercial method (Detect-TB kit, Labtest/MG-Brazil). All DNA samples were amplified by qPCR for IS6110 region (IS6110-qPCR/SYBR Green assay). Out of 60 samples, 40 were positive for TB; of these, all had positive results when extracted by sonication (100%) and 80% when extracted by the commercial method. The limit of detection (LOD) of Mycobacterium tuberculosis (H37Rv strain) by qPCR was 14 CFU/mL when the DNA was extracted by sonication, compared to countless colonies when extracted by commercial kit. In conclusion, the sonication protocol (without purification step) proved to be a simple, fast, and suitable method for obtaining DNA for use in qPCR from sputum samples.