Lateral flow assay for rapid differentiation of Mycobacterium tuberculosis complex and 97 species of mycobacteria other than tuberculosis grown in Löwenstein-Jensen and TK-SLC medium

BACKGROUND: Mycobacterial antigen MPB64 is a secretory protein specific for Mycobacterium tuberculosis complex. A lateral flow immunochromatographic assay (ICA) is a method used for the rapid differentiation of M. tuberculosis complex. AIM: We aimed to evaluate the performance of ICA in rapid differentiation of M. tuberculosis complex from 97 Mycobacterium species other than tuberculosis (MOTT), which are grown in Lφwenstein-Jensen and TK-selective (SLC) medium. MATERIALS AND METHODS: The study was performed in our laboratory between January 2009 and January 2010. A total of 394 isolates consisting of reference strains of 34 M. tuberculosis from World Health Organization (WHO) collection, 97 different MOTT bacilli, 7 Mycobacterium bovis BCG substrains and total 256 clinical Mycobacterium isolates were tested by ICA, which is based on anti-MPB64 monoclonal antibodies. All the strains were inoculated onto a TK-SLC (selective) medium and Lowenstein-Jensen medium. TK-SLC is a new rapid mycobacterial culture medium that indicates mycobacterial growth by colour change. RESULTS: The growth of mycobacterial strains was observed in 10-12 days on TK-SLC medium. ICA test was performed in 15 minutes. All strains belonging to M. tuberculosis complex group were found positive and all MOTT species were found negative on ICA slides. The results were confirmed with nucleic acid amplification by polymerase chain reaction (PCR) using primers specific for M. tuberculosis complex. CONCLUSION: With the additive effect of growth on TK-SLC medium in 10-12 days, the mycobacterial antigen MPB64 is a very useful and specific tool in rapid differentiation of M. tuberculosis and MOTT grown in culture.