Simultaneous detection of Mycobacterium tuberculosis complex and resistance to Rifampicin and Isoniazid by MDR/MTB ELITe MGB® Kit for the diagnosis of tuberculosis

The MDR/MTB ELITe MGB® Kit on the ELITe InGenius® platform (ELITechGroup SpA, Italy) is the first system for simultaneous detection of the Mycobacterium tuberculosis complex (MTBc) genome and the main mutations responsible for resistance to Isoniazid (inhA, katG) and Rifampicin (rpoB), from decontaminated and heat inactivated samples. In this study we compared the performance of the MDR/MTB ELITe MGB® Kit (ELITe) with culture in 100 pulmonary and 160 extra-pulmonary samples. The sensitivity and specificity of ELITe compared to culture for pulmonary samples were 98.0% and 98.0% respectively; for extrapulmonary samples the overall sensitivity was 86.3% (80% for urine, 85% for biopsy and gastric aspirate and 95% for cavitary fluid) and specificity was 100%. Genotypic Isoniazid and Rifampicin susceptibility typing was feasible in 96% of sputum MTBc-positive samples and 43% of extra-pulmonary samples; all samples were found to be drug susceptible by phenotypic and ELITe (100% agreement). Detection of mutations in the rpoB, kat G or inhA genes was evaluated on 300 spiked samples (60 per biological matrix) and all resistance profiles were correctly identified by ELITe. Molecular agreement between ELITe and Xpert was 98.0% and 93.3% for pulmonary and extra-pulmonary samples, respectively. In conclusion, our results provide evidence to support the use of MDR/MTB ELITe MGB® Kit in combination with ELITe InGenius® for the diagnosis of MTBc and the detection of Rifampicin and Isoniazid resistance-related mutations in both pulmonary and extra-pulmonary samples. This system simplifies the laboratory workflow, shortens report time and is an aid in choosing appropriate therapeutic treatment and patient management.