title: Rapid detection of rifampicin resistance in Mycobacterium tuberculosis by high-resolution melting curve analysis.
abstract: METHODS
  High-resolution melting curve analysis (HRMA) can be used to screen for mutations in genes without the need for specific probes, with low turnaround time and high cost-effectiveness.
  
  
  OBJECTIVE
  To detect the sensitivity and specificity of a line-probe assay (LPA) and HRMA in comparison with BACTEC™ MGIT™ 960 for the detection of rifampicin (RMP) resistance.
  
  
  METHODS
  A total of 219 Mycobacterium tuberculosis isolates tested by MGIT 960 for RMP susceptibility were tested with HRMA and LPA. Discordant samples were processed for sequencing of the RMP resistance-determining region (RRDR) of the rpoB gene.
  
  
  RESULTS
  HRMA identified 93 of 103 (90.3%) isolates that were resistant and 113/116 (97.4%) that were susceptible on MGIT 960, with a sensitivity and specificity of respectively 90.3% and 97.4%. HRMA identified 117/119 (98.3%) LPA-susceptible and 94/100 (94%) resistant isolates, with 98.3% specificity and 94% sensitivity. Two isolates that were susceptible on LPA but resistant on HRMA showed silent mutations at 539 and 541 codons on sequencing, while 6 isolates that were susceptible on HRMA but resistant on LPA showed D516V (n = 4) and H526C/D (n = 2) mutations. Four isolates (3.9%) that were resistant on MGIT were susceptible on all three genotypic methods, which could be due to mutations outside the RRDR or efflux pumps.
  
  
  CONCLUSIONS
  HRMA shows good potential as a rapid screening tool for the detection of drug resistance.
authors.affiliation: Department of Microbiology and Immunology, Sawai Man Singh Medical College, Jaipur, India.
authors.forename: B
authors.initials: B
authors.lastname: Malhotra
authors.affiliation: Department of Microbiology and Immunology, Sawai Man Singh Medical College, Jaipur, India.
authors.forename: S
authors.initials: S
authors.lastname: Goyal
authors.affiliation: Department of Microbiology and Immunology, Sawai Man Singh Medical College, Jaipur, India.
authors.forename: S
authors.initials: S
authors.lastname: Bhargava
authors.affiliation: Department of Microbiology and Immunology, Sawai Man Singh Medical College, Jaipur, India.
authors.forename: P V J
authors.initials: PV
authors.lastname: Reddy
authors.affiliation: Department of Microbiology and Immunology, Sawai Man Singh Medical College, Jaipur, India.
authors.forename: A
authors.initials: A
authors.lastname: Chauhan
authors.affiliation: Department of Microbiology and Immunology, Sawai Man Singh Medical College, Jaipur, India.
authors.forename: J
authors.initials: J
authors.lastname: Tiwari
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D008826:Microbial Sensitivity Tests / Q000379:methods; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects*; D012293:Rifampin / Q000494:pharmacology*; D012680:Sensitivity and Specificity
chemical_list: D000995:Antitubercular Agents; D012293:Rifampin