title: Isoniazid and rifampin drug susceptibility testing: application of 2,3,5-triphenyl tetrazolium chloride assay and microscopic-observation drug-susceptibility assay directly on Ziehl-Neelsen smear positive sputum specimens.
abstract: The current study was aimed to evaluate the performance of direct 2,3,5-triphenyl tetrazolium chloride assay and direct microscopic observation drug susceptibility assay with indirect Löwenstein-Jensen proportion method directly on Ziehl-Neelsen smear positive sputum specimens.
  
  
  METHODS
  Direct acid fast bacilli smear positive sputum specimens (n=264) were subjected to isoniazid and rifampicin drug susceptibility testing by direct 2,3,5-triphenyl tetrazolium chloride assay, direct microscopic observation drug susceptibility assay, and the performances were compared with indirect Löwenstein-Jensen proportion method.
  
  
  RESULTS
  The direct 2,3,5-triphenyl tetrazolium chloride assay demonstrated an overall sensitivity, specificity, positive predictive value, and negative predictive value of 99.2%, 82.4%, 99.2%, and 88.5%, respectively, for the detection of isoniazid and rifampicin resistant Mycobacterium tuberculosis isolates when compared to indirect Löwenstein-Jensen proportion method. Likewise, the overall sensitivity, specificity, positive predictive value and negative predictive value of direct microscopic observation drug susceptibility assay were 98.8%, 82.4%, 99.2%, and 78.2%, respectively.
  
  
  CONCLUSIONS
  The direct 2,3,5-triphenyl tetrazolium chloride assay was found to be an economical alternative method for the rapid and accurate detection of isoniazid and rifampicin resistance from direct acid fast bacilli smear positive sputum specimens.
authors.affiliation: Department of Microbiology, M.M.I.M.S.R., MM University, Mullana, Ambala 133207, India. Electronic address: shinup1983@gmail.com.
authors.forename: Pottathil
authors.initials: P
authors.lastname: Shinu
authors.affiliation: Department of Microbiology, M.M.I.M.S.R., MM University, Mullana, Ambala 133207, India.
authors.forename: Varsha
authors.initials: V
authors.lastname: Singh
authors.affiliation: Department of Pharmaceutical Sciences, College of Clinical Pharmacy, King Faisal University, Al-Ahsa, Saudi Arabia.
authors.forename: Anroop
authors.initials: A
authors.lastname: Nair
mesh_terms: D000328:Adult; D000995:Antitubercular Agents / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007538:Isoniazid / Q000494:pharmacology*; D008297:Male; D008826:Microbial Sensitivity Tests / Q000379:methods*; D009169:Mycobacterium tuberculosis / Q000187:drug effects; D012293:Rifampin / Q000494:pharmacology*; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D013778:Tetrazolium Salts; D014397:Tuberculosis, Pulmonary / Q000382:microbiology
chemical_list: D000995:Antitubercular Agents; D013778:Tetrazolium Salts; C009591:triphenyltetrazolium; D007538:Isoniazid; D012293:Rifampin
keywords: Evaluation; Löwenstein–Jensen; Rapid; Tuberculosis