Immunochromatographic detection of MPB64 secreted from active BCG by heating: toward same-day diagnosis of tuberculosis.

We propose a new detection method for a tuberculosis-specific protein, MPB64, obtained from active bacillus Calmette-Guerin (BCG) by heating. When BCG was included in solution at a concentration >2.75 x 10(4) CFU/ml, our method for collecting MPB64 through heating active BCG combined with an immunochromatographic assay detected active bacilli within 2.5 h. By contrast, a culture test, which is the gold standard for tuberculosis diagnosis, does not provide results for between 1 week and 2 months. The rapid tests based on PCR have some drawbacks, for example they detect DNA from both active and latent (or even dead) tubercle bacilli. Therefore, our method may pave the way toward detecting only active tubercle bacilli at a reasonable cost and providing same-day diagnosis. METHOD SUMMARY BCG is heated to secrete a specific Mycobacterium tuberculosis protein, MPB64, which is an indicator of active tubercle bacilli. MPB64 is detected by an immunochromatographic assay using platinum-gold colloid. The time from preparation of specimens to detection of MPB64 (i.e., active tubercle bacilli) is only 2.5 h.