Author/Authors :
Stevens, Wendy Department of Molecular Medicine and Haematology, Faculty of Health Sciences - School of Pathology - University of the Witwatersrand - Johannesburg, South Africa , Chikaonda, Tarsizio Department of Molecular Medicine and Haematology, Faculty of Health Sciences - School of Pathology - University of the Witwatersrand - Johannesburg, South Africa , Ketseoglou, Irene Department of Molecular Medicine and Haematology, Faculty of Health Sciences - School of Pathology - University of the Witwatersrand - Johannesburg, South Africa , Scott, Lesley Department of Molecular Medicine and Haematology, Faculty of Health Sciences - School of Pathology - University of the Witwatersrand - Johannesburg, South Africa , Papathanasopoulos, Maria A. Department of Molecular Medicine and Haematology, Faculty of Health Sciences - School of Pathology - University of the Witwatersrand - Johannesburg, South Africa , Nguluwe, Nelson UNC Project - Lilongwe, Malawi , Krysiak, Robert UNC Project - Lilongwe, Malawi , Thengolose, Isaac UNC Project - Lilongwe, Malawi , Rosenberg, Nora E. UNC Project - Lilongwe, Malawi , Stanley, Christopher UNC Project - Lilongwe, Malawi , Hoffman, Irving F. UNC Project - Lilongwe, Malawi , Hosseinipour, Mina UNC Project - Lilongwe, Malawi , Nyakwawa, Felix Malawi National Tuberculosis Programme - Lilongwe, Malawi , Mpunga, James Malawi National Tuberculosis Programme - Lilongwe, Malawi
Abstract :
Availability and access to the detection of resistance to anti-tuberculosis drugs remains a significant challenge in Malawi due to limited diagnostic services. The Xpert® MTB/RIF can detect Mycobacterium tuberculosis and resistance to rifampicin in a single, rapid assay. Rifampicin-resistant M. tuberculosis has not been well studied in Malawi.
Objectives
We aimed to determine mutations in the rifampicin resistance determining region (RRDR) of the rpoB gene of M. tuberculosis strains which were defined as resistant to rifampicin by the Xpert MTB/RIF assay.
Methods
Rifampicin-resistant isolates from 43 adult patients (≥ 18 years) from various districts of Malawi were characterised for mutations in the RRDR (codons 507–533) of the rpoB gene by DNA sequencing.
Results
Mutations were found in 37/43 (86%) of the resistant isolates in codons 511, 512, 513, 516, 522, 526 and 531. The most common mutations were in codons 526 (38%), 531 (29.7%) and 516 (16.2%). Mutations were not found in 6/43 (14%) of the resistant isolates. No novel rpoB mutations other than those previously described were found among the rifampicin-resistant M. tuberculosis complex strains.
Conclusion
This study is the first to characterise rifampicin resistance in Malawi. The chain-termination DNA sequencing employed in this study is a standard method for the determination of nucleotide sequences and can be used to confirm rifampicin resistance obtained using other assays, including the Xpert MTB/RIF. Further molecular cluster analysis, such as spoligotyping and DNA finger printing, is still required to determine transmission dynamics and the epidemiological link of the mutated strains.
