Evaluation of a tetrazolium salt test to determine absence of live mycobacteria in tuberculin purified protein derivative.
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.
Bedwell
J
J
Division of Bacteriology, National Institute for Biological Standards and Control, Blanche Lane, South Mimms, Potters Bar, Hertfordshire, EN6 3QG, UK.
Kairo
S K
SK
Corbel
M J
MJ
D005069:Evaluation Studies as Topic; D009161:Mycobacterium / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D013778:Tetrazolium Salts; D014373:Tuberculin / Q000737:chemistry*
D013778:Tetrazolium Salts; D014373:Tuberculin