title: [Heteroresistance in Mycobacteria tuberculosis is an important factor for the inconsistency between the results of phenotype and genotype drug susceptibility tests].
abstract: OBJECTIVE
  To investigate the impact of heteroresistance on the results of genotype drug susceptibility test for Mycobacterium tuberculosis (M. tuberculosis).
  
  
  METHODS
  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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  Heteroresistance is an important factor for the inconsistency between the results of phenotype and genotype drug susceptibility tests. For improving the rapid detection of drug resistant tuberculosis, novel genotypic drug susceptibility test methods with higher sensitivity should be developed and applied.
authors: Key Laboratory of Medical Molecular Virology, Institutes of Biomedical Sciences and Institute of Medical Microbiology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
authors: Xu
authors: X
authors: Gao
authors: Jing
authors: J
authors: Li
authors: Qingyun
authors: Q
authors: Liu
authors: Xin
authors: X
authors: Shen
authors: Jian
authors: J
authors: Mei
authors: Key Laboratory of Medical Molecular Virology, Institutes of Biomedical Sciences and Institute of Medical Microbiology, Shanghai Medical College, Fudan University, Shanghai 200032, China. Email: qgao99@yahoo.com.
authors: Qian
authors: Q
authors: Gao
mesh_terms: D004269:DNA, Bacterial; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D018740:Genetic Heterogeneity; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000235:genetics*; D015242:Ofloxacin / Q000494:pharmacology; D010641:Phenotype; D016133:Polymerase Chain Reaction / Q000379:methods
chemical_list: D004269:DNA, Bacterial; D015242:Ofloxacin