title: Multicenter study of MTT and resazurin assays for testing susceptibility to first-line anti-tuberculosis drugs.
abstract: OBJECTIVE
  A multicentre evaluation was performed to assess two rapid low-cost methods, MTT (3-[4.5-dimethylthiazol-2-yl]-2.5-diphenyltetrazolium bromide) and resazurin assays, for testing the susceptibility of Mycobacterium tuberculosis to the first-line anti-tuberculosis drugs rifampicin (RMP), isoniazid (INH), ethambutol (EMB) and streptomycin (SM).
  
  
  METHODS
  Thirty coded M. tuberculosis strains were sent to seven laboratories located in Latin America, representing six countries. Each site performed the colorimetric assays, MTT and resazurin, blind for the first-line drugs RMP, INH, EMB and SM. The minimum inhibitory concentration results obtained were compared to the conventional proportion method on Lowenstein-Jensen medium.
  
  
  RESULTS
  After establishing the breakpoint concentrations, excellent results were obtained for RMP, INH and EMB, with levels of specificity and sensitivity of between 96% and 99%.
  
  
  CONCLUSIONS
  MTT and resazurin assays are promising, accessible new alternative methods for middle- and low-resource countries that need low-cost methods to perform rapid susceptibility testing of M. tuberculosis to key anti-tuberculosis drugs.
authors.affiliation: Mycobacteriology Unit, Institute of Tropical Medicine, Antwerp, Belgium. amartin@itg.be
authors.forename: A
authors.initials: A
authors.lastname: Martin
authors.forename: N
authors.initials: N
authors.lastname: Morcillo
authors.forename: D
authors.initials: D
authors.lastname: Lemus
authors.forename: E
authors.initials: E
authors.lastname: Montoro
authors.forename: M A da Silva
authors.initials: MA
authors.lastname: Telles
authors.forename: N
authors.initials: N
authors.lastname: Simboli
authors.forename: M
authors.initials: M
authors.lastname: Pontino
authors.forename: T
authors.initials: T
authors.lastname: Porras
authors.forename: C
authors.initials: C
authors.lastname: León
authors.forename: M
authors.initials: M
authors.lastname: Velasco
authors.forename: L
authors.initials: L
authors.lastname: Chacon
authors.forename: L
authors.initials: L
authors.lastname: Barrera
authors.forename: V
authors.initials: V
authors.lastname: Ritacco
authors.forename: F
authors.initials: F
authors.lastname: Portaels
authors.forename: J C
authors.initials: JC
authors.lastname: Palomino
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D004396:Coloring Agents; D024881:Drug Resistance, Bacterial; D006801:Humans; D007202:Indicators and Reagents; D007843:Latin America; D008826:Microbial Sensitivity Tests; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000472:pathogenicity; D010078:Oxazines; D012016:Reference Values; D015203:Reproducibility of Results; D013778:Tetrazolium Salts; D013844:Thiazoles; D014397:Tuberculosis, Pulmonary / Q000188:drug therapy; D014966:Xanthenes
chemical_list: D000995:Antitubercular Agents; D004396:Coloring Agents; D007202:Indicators and Reagents; D010078:Oxazines; D013778:Tetrazolium Salts; D013844:Thiazoles; D014966:Xanthenes; C005843:resazurin; C022616:thiazolyl blue