DETECTION OF MYCOBACTERIAL ANTIGENS PRESENT IN SHORT-TERM CULTURE MEDIA USING PARTICLE COUNTING IMMUNOASSAY

Particle counting immunoassay (PACIA) was compared with the BACTEC(R) system for detecting mycobacterial growth after short-term culture and was used to identify M. tuberculosis. The latex particles were coated with polyclonal anti-BCG or with specific 2A1-2 monoclonal antibodies . Bottles containing nonradioactive Middlebrook 7H9 liquid medium and BACTEC 12B vials were inoculated with equal amounts of mycobacteria fr om four reference strains (M. tuberculosis, M. kansasii, M. avium, and M. xenopi). Using anti-BCG, PACIA detected mycobacterial antigens 3 t o 6 days before the BACTEC system. M. tuberculosis was differentiated from the other mycobacteria using 2A1-2. Seventeen clinical samples we re also studied. In the same 10, the two techniques detected mycobacte ria, PACIA with anti-BCG after 9 days and BACTEC 1 to 5 days later. Fo r 9 of the 10 samples, PACIA with 2A1-2 detected M. tuberculosis after 20 days, a result confirmed with the AccuProbe(R) system. M. xenopi w as biochemically identified in Specimen 10. Nonmycobacterial diseases were diagnosed in the 7 remaining unreactive specimens. We conclude th at PACIA detects mycobacterial growth earlier than BACTEC and that M. tuberculosis can be distinguished from other mycobacteria in PACIA per formed with specific monoclonal antibodies.