Phenotypic and Genotypic Characterization of Multi-Drug Resistant Mycobacterium tuberculosis

Abstract

This study characterized multi-drug resistant M. tuberculosis phenotypically by LJ-proportion method and genotypically by GenoType MTBDRplus LPA. Out of the forty M. tuberculosis isolates tested, two (5.0%) were found to be multi-drug resistant by the LJ proportion method, and one (2.5%) was MDR by LPA. None was found to be mono-resistant to any of the drugs by LJ; however, one isolate was mono-resistant to RIF and one was mono-resistant to INH by LPA. Comparison of GenoType MTBDRplus LPA and phenotypic LJ-proportion methods showed that one isolate was mono-resistant to RIF and one was mono-resistant to INH by LPA, while one and two MDR-TB isolates, respectively, were characterized by genotypic and phenotypic methods. The remaining isolates were found to be pan-susceptible by both methods. One isolate was characterized as MDR with bands at rpoβ MUT2A region and inhA MUT2 corresponding to H526Y and A16G mutations, respectively. Rifampicin mono-resistance with a band at rpoβ MUT3 corresponding to S531L was found in one isolate. Also, isoniazid mono-resistance was observed in one isolate with inhA MUT2 band corresponding to the A16G mutation. This study has shown an overall high prevalence of MDR-TB in the study area, which needs to be urgently addressed. Laboratory facilities for rapid drug resistance detection are needed across the country for early and accurate diagnosis of TB and drug-resistant cases. This remains an important step in managing TB drug resistance in Nigeria.