According to the World Health Organisation (WHO) there were 8.6 million people diagnosed with Tuberculosis (TB) worldwide in 2012. Of these cases, there were 450,000 Multidrug-resistant TB (MDR-TB) and 43,200 extensively drug- resistant TB (XDR-TB) strains detected. Early diagnosis of MDR and XDR-TB is important for effective treatment and management.
The standard treatment of TB includes four 1st line drugs Isoniazid (INH), Rifampicin (RIF), Pyrazinamide and Ethambutol. Resistance to 2 of 4 of the 1st line drugs classifies the isolate as MDR-TB. Further resistance to fluoroquinolones and injectable drugs classifies the isolate as XDR-TB. These highly drug resistant strains present a clear public health concern due to the risk of transmission of MDR-TB and XDR-TB if not detected early.
A study was conducted to evaluate the sensitivity and specificity of the Seegene AnyplexTMII MTB/MDR/XDR assay using the CFX96 Real-time PCR platform (BIO-RAD), against known M.tb culture positive and clinical samples. The assay is designed to detect Mtb along with specific resistance- causing point mutations in rpoB, inhA promoter, katG, gyrA, rrs and eis promoter genes using melting temperature analysis.
The Seegene AnyplexTMII MTB/MDR/XDR kit was tested in parallel at the NSW Mycobacterium Reference Laboratory (MRL) against standard methods of identification and susceptibility testing.
A total of 47 direct clinical samples and 87 M.tb culture positive samples were tested. The kit was successful in detecting M.tb and specific resistance- causing point mutations from culture samples. Sensitivity and specificity for clinical samples were inconsistent.
Overall, the assay is recommended for testing solid and liquid culture material for the detection of M.tb susceptible strains, MDR-TB and XDR-TB. The usage of the assay on clinical samples produces inconsistent results.