First evaluation of an improved assay for molecular genetic detection of tuberculosis as well as rifampin and isoniazid resistances

Abstract

The commercially available line probe assay MTBDRplus 2.0 (Hain Lifescience, Nehren, Germany) was evaluated for its ability to detect Mycobacterium tuberculosis complex (MTBC) and mutations conferring resistance to rifampin (RMP) and isoniazid (INH) directly in smear-negative and smear-positive pulmonary clinical specimens under routine laboratory conditions. A total of 348 samples originating from Moldova, a high-incidence country for tuberculosis (TB), were investigated. Two hundred fifty-seven (73.9%) were smear negative, 12 samples were excluded, and 81 (23.3%) were smear positive. Two DNA extraction methods were applied. Compared to culture and clinical data as the reference standard (adapted from Vadwai V et al., J. Clin. Microbiol. 49:2540-2545, 2011), overall sensitivity and specificity were 87.6 and 99.2%, respectively. One hundred four of the 257 smear-negative samples turned out to be culture positive, and 20 were MTBC culture negative but were positive based on clinical symptoms. The combined sensitivity and specificity in the subgroup of smear-negative samples were calculated to be 79.8 and 99.2%, respectively. MTBDRplus 2.0 detected RMP and INH resistance with sensitivity and specificity of 94.3 and 96.0%, respectively. In conclusion, the MTBDRplus 2.0 assay is a rapid and highly sensitive test for the detection of M. tuberculosis strains from smear-positive and -negative clinical specimens and provides additional information on RMP and INH resistance status, which can easily be included in routine laboratory work flow.

Fig 1

Example of a developed MTBDRplus 2.0 strip. Line 1, MDR strain (ΔrpoB WT8, rpoB MUT3, ΔkatG WT, katG MUT1, ΔinhA WT1, inhA MUT1); line 2, MDR strain (ΔrpoB WT3, ΔrpoB WT4, rpoB MUT1, ΔkatG WT, katG MUT1); line 3, MDR strain (ΔrpoB WT8, rpoB MUT3, ΔkatG WT, katG MUT1, ΔinhA WT1, inhA MUT1); line 4, MDR strain (ΔrpoB WT8, rpoB MUT3, ΔkatG WT, katG MUT1); and line 5, WT strain.