Michelle Maharaj
University of KwaZulu-Natal, South Africa
Title: Evaluation of the BD MGITâ„¢ TBc identifi cation test for confi rmation of Mycobacterium tuberculosis complex (MTBC) from isolates cultured on solid media (7h11)
Biography
Biography: Michelle Maharaj
Abstract
Background & Objectives: Globally, tuberculosis is a disease of major public health concern. The Human Immunodeficiency Virus (HIV) epidemic has increased the incidence of infection with nontuberculous mycobacteria (NTM). Differentiation of Mycobacterium tuberculosis complex (MTBC) isolates from NTM is critical for accurate management and improved patient outcomes. MPT64 is a mycobacterial protein secreted only by MTBC and has been shown to differentiate MTBC from NTM. BD MGIT TBc identification test (TBc ID) is a cost effective, rapid immunochromatographic assay for qualitative detection of MPT64 antigen. The BD TBc ID kit is currently validated for use on MGIT broth media. We evaluated the performance of the TBc ID for rapid identification of MTBC in samples cultured on Middlebrook 7H11 solid media.
Method: Twenty three clinical isolates (14 sputum; five blood cultures; two gastric washings; one bronchial lavage and one CSF) and two ATCC control strains (25177 and 13950) were cultured on solid media. Colonies from 7H11 plates were emulsified in 200 μl of 7H9 broth and 100 μl was then added to the sample window to observe the development of a purple band within 15 minutes. These results were compared with Hain Genotype MTBDRplus V2 assay. Interpretation of both tests was done in accordance to the manufacture guidelines.
Results: Of the 23 samples, 18 were MPT64ag positive and five were negative. For all 18 positive samples, the MTBDRplus V2 assay confirmed the presence MTBC. The five negative samples were also negative on the MTBDRplus V2 assay. This comparison demonstrated 100% concordance between the MTBDRplus V2 assay and BD MGIT™ TBc identification test for identification of MTBC.
Conclusion: Whilst the numbers were small, our results showed a 100% correlation between the two tests demonstrating preliminary suitability of BD MGIT TBc identification test for rapid identification of MTBC from MB 7H11 colonies.