title: Rapid screening of rpoB and katG mutations in Mycobacterium tuberculosis isolates by high-resolution melting curve analysis.
abstract: BACKGROUND
  Early detection of multidrug-resistant tuberculosis (MDR-TB) is essential to prevent its transmission in the community and initiate effective anti-TB treatment regimen.
  
  
  METHODS
  High-resolution melting curve (HRM) analysis was evaluated for rapid detection of resistance conferring mutations in rpoB and katG genes. We screened 95 Mycobacterium tuberculosis clinical isolates including 20 rifampin resistant (RIF-R), 21 isoniazid resistant (INH-R) and 54 fully susceptible (S) isolates determined by proportion method of drug susceptibility testing. Nineteen M. tuberculosis isolates with known drug susceptibility genotypes were used as references for the assay validation. The nucleotide sequences of the target regions rpoB and katG genes were determined to investigate the frequency and type of mutations and to confirm HRM results.
  
  
  RESULTS
  HRM analysis of a 129-bp fragment of rpoB allowed correct identification of 19 of the 20 phenotypically RIF-R and all RIF-S isolates. All INH-S isolates generated wild-type HRM curves and 18 out of 21 INH-R isolates harboured any mutation in 109-bp fragment of katG exhibited mutant type HRM curves. However, 1 RIF-R and 3 INH-R isolates were falsely identified as susceptible which were confirmed for having no mutation in their target regions by sequencing. The main mutations involved in RIF and INH resistance were found at codons rpoB531 (60% of RIF-R isolates) and katG315 (85.7% of INH-R isolates), respectively.
  
  
  CONCLUSIONS
  HRM was found to be a reliable, rapid and low cost method to characterise drug susceptibility of clinical TB isolates in resource-limited settings.
authors.forename: M
authors.initials: M
authors.lastname: Haeili
authors.forename: A I
authors.initials: AI
authors.lastname: Fooladi
authors.forename: S Z
authors.initials: SZ
authors.lastname: Bostanabad
authors.forename: D D
authors.initials: DD
authors.lastname: Sarokhalil
authors.forename: F
authors.initials: F
authors.lastname: Siavoshi
authors.affiliation: School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: M M
authors.initials: MM
authors.lastname: Feizabadi
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D002374:Catalase / Q000235:genetics*; D003365:Costs and Cost Analysis; D012321:DNA-Directed RNA Polymerases; D024881:Drug Resistance, Bacterial; D005838:Genotype; D006801:Humans; D008403:Mass Screening / Q000191:economics / Q000379:methods; D025202:Molecular Diagnostic Techniques / Q000191:economics / Q000379:methods*; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000235:genetics*; D013997:Time Factors; D044366:Transition Temperature; D018088:Tuberculosis, Multidrug-Resistant / Q000175:diagnosis*
chemical_list: D001426:Bacterial Proteins; C505805:rpoB protein, Mycobacterium tuberculosis; D002374:Catalase; C480353:katG protein, Mycobacterium tuberculosis; D012321:DNA-Directed RNA Polymerases