title: Evaluation of a tetrazolium salt test to determine absence of live mycobacteria in tuberculin purified protein derivative.
abstract: Current methodology to determine absence of live mycobacteria in tuberculin purified protein derivative (PPD) takes up to 8 weeks to perform and may also involve testing on animals. In this paper we describe an in vitro test utilising the tetrazolium salt, 2,3-bis-(2-methoxy-4-nitro-5-sulphenyl)-(2H)-tetrazolium-5-carboxanilide (XTT) to monitor the absence of live Mycobacterium tuberculosis (Mtb) in PPD. In the presence of live cells XTT is converted to a coloured formazan product that can be measured spectrophotometrically. Live mycobacteria present in spiked PPD were detected by a marked change in optical density above background levels. This test is easy to perform and is complete in just 48 hr.
authors.affiliation: Division of Bacteriology, National Institute for Biological Standards and Control, Blanche Lane, South Mimms, Potters Bar, Hertfordshire, EN6 3QG, UK.
authors.forename: J
authors.initials: J
authors.lastname: Bedwell
authors.forename: S K
authors.initials: SK
authors.lastname: Kairo
authors.forename: M J
authors.initials: MJ
authors.lastname: Corbel
mesh_terms: D005069:Evaluation Studies as Topic; D009161:Mycobacterium / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D013778:Tetrazolium Salts; D014373:Tuberculin / Q000737:chemistry*
chemical_list: D013778:Tetrazolium Salts; D014373:Tuberculin