['To investigate the impact of heteroresistance on the results of genotype drug susceptibility test for Mycobacterium tuberculosis (M. tuberculosis).', 'A total of 80 phenotype ofloxacin-resistant M. tuberculosis isolates obtained from Shanghai Municipal Centers for Disease Control and Prevention were included in the study. The mutations of gyrA and gyrB in each isolate were identified by gene sequencing. Molecular cloning and multiplex real-time PCR melting curve assay were applied to analyze the presence of heteroresistance in those isolates that had showed no mutations by gene sequencing.', 'The sequencing results showed that 15 of these 80 isolates had no mutations in gyrA or gyrB. By analyzing the sequencing chromatogram, we found that 7 of the 15 isolates had gyrA mutations. By molecular cloning and melting curve assay, we identified another 7 isolates with low frequency mutations in gyrA that had been previously identified. In total, 14 isolates with heteroresistance were detected in these 15 isolates. The consistency between the results of phenotype and genotype drug susceptibility tests was increased from 81.3% (65/80) to 98.8% (79/80).'] Is [ Heteroresistance in Mycobacteria tuberculosis an important factor for the inconsistency between the results of phenotype and genotype drug susceptibility tests ]?