title: Evaluation of nitrate reduction assay, resazurin microtiter assay and microscopic observation drug susceptibility assay for first line antitubercular drug susceptibility testing of clinical isolates of M. tuberculosis.
abstract: BACKGROUND
  Drug resistant tuberculosis (TB) is a growing concern worldwide. Early detection of multidrug-resistant Mycobacterium tuberculosis is of primary importance for both patient management and infection control. Optimal method for identifying drug-resistant M. tuberculosis in a timely and affordable way in resource-limited settings is not yet available.
  
  
  OBJECTIVE
  This study evaluated; nitrate reductase assay (NRA), resazurin microtiter assay (REMA) and microscopic observation drug susceptibility assay (MODS) against the conventional 1% proportion method (PM) for the detection of resistance to first line antitubercular drugs, in M. tuberculosis clinical isolates.
  
  
  METHODS
  A total of one hundred and five clinical isolates of M. tuberculosis; 50 pan sensitive and 55 pan resistant were tested with NRA, REMA and MODS. The 1% proportion method on Lowenstein-Jensen medium was used as reference test.
  
  
  RESULTS
  Of all three methods which were tested NRA was found to be most sensitive and specific. Sensitivity for rifampicin resistance detection was 100%, 94.55% and 92.73% by NRA, REMA and MODS respectively. NRA and REMA were found to be 100% specific, while the MODS was 98% specific for detection of rifampicin resistance. Test results with all these methods were obtained within 8-14 days.
  
  
  CONCLUSIONS
  Rapid non-conventional and inexpensive methods may serve as a replacement for 1% proportion method in resource limited settings.
authors: Department of Microbiology, C. S. M. Medical University, Lucknow-226003, India.
authors: Pratima
authors: P
authors: Dixit
authors: Urmila
authors: U
authors: Singh
authors: Pratibha
authors: P
authors: Sharma
authors: Amita
authors: A
authors: Jain
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000032:analysis / Q000378:metabolism; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D008853:Microscopy / Q000379:methods*; D009169:Mycobacterium tuberculosis / Q000737:chemistry / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D050901:Nitrate Reductase / Q000032:analysis* / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D010078:Oxazines / Q000032:analysis; D012680:Sensitivity and Specificity; D014376:Tuberculosis / Q000382:microbiology*; D014966:Xanthenes / Q000032:analysis
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins; D009566:Nitrates; D010078:Oxazines; D014966:Xanthenes; C005843:resazurin; D050901:Nitrate Reductase