Evaluation of FluoroType MTB for direct detection of Mycobacterium tuberculosis complex and GenoType MTBDRplus for determining rifampicin and isoniazid resistance

Abstract

In recent years, several molecular methods have been introduced for diagnosis of Mycobacterium tuberculosis complex (MTBC), and detecting the drug resistance in clinical specimens. The FluoroType MTB (FT MTB) assay uses real-time polymerase chain reaction (PCR) to detect MTBC in clinical specimens. GenoType MTBDRplus is a line probe assay which detects MTBC, as well as rifampicin, and isoniazid resistance. In this study, the diagnostic performances of FT MTB and GenoType MTBDRplus were evaluated. In total, 247 specimens (124 respiratory, 123 non-respiratory) were analyzed comparing mycobacterial growth methods and FT MTB. GenoType MTBDRplus was used for the specimens positive for MTBC. In all, 23 (9.3%) of 247 specimens were positive for both the culture and FT MTB assay; therefore, the GenoType MTBDRplus assay was performed on 23 clinical specimens. The results were concordant with the drug susceptibility test results. The FT MTB assay provided quick and reliable direct detection of MTBC from the clinical specimens with high sensitivity (95.8%) and specificity (100%). Although the performance of GenoType MTBDRplus was problematic in clinical specimens with mycobacterial levels below the detection limits of the assay, it was a reliable test for cultivated specimens.

Keywords

• Drug resistance
• drug susceptibility testing
• isoniazid
• rifampicin
• mycobacteria
• Mycobacterium tuberculosis complex