Original Research

Molecular characterisation of rifampicin-resistant Mycobacterium tuberculosis strains from Malawi

Tarsizio Chikaonda, Irene Ketseoglou, Nelson Nguluwe, Robert Krysiak, Isaac Thengolose, Felix Nyakwawa, Nora E. Rosenberg, Christopher Stanley, James Mpunga, Irving F. Hoffman, Maria A. Papathanasopoulos, Mina Hosseinipour, Lesley Scott, Wendy Stevens
African Journal of Laboratory Medicine | Vol 6, No 2 | a463 | DOI: https://doi.org/10.4102/ajlm.v6i2.463 | © 2017 Tarsizio Chikaonda, Irene Ketseoglou, Nelson Nguluwe, Robert Krysiak, Isaac Thengolose, Felix Nyakwawa, Nora E. Rosenberg, Christopher Stanley, James Mpunga, Irving F. Hoffman, Maria A. Papathanasopoulos, Mina Hosseinipour, Lesley Scott, Wendy Stevens | This work is licensed under CC Attribution 4.0
Submitted: 08 April 2016 | Published: 31 March 2017

About the author(s)

Tarsizio Chikaonda, Department of Molecular Medicine and Haematology, Faculty of Health Sciences, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa and UNC Project, Lilongwe, Malawi
Irene Ketseoglou, Department of Molecular Medicine and Haematology, Faculty of Health Sciences, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
Nelson Nguluwe, UNC Project, Lilongwe, Malawi
Robert Krysiak, 2UNC Project, Lilongwe, Malawi
Isaac Thengolose, UNC Project, Lilongwe, Malawi
Felix Nyakwawa, Malawi National Tuberculosis Programme, Lilongwe, Malawi
Nora E. Rosenberg, UNC Project, Lilongwe, Malawi
Christopher Stanley, UNC Project, Lilongwe, Malawi
James Mpunga, Malawi National Tuberculosis Programme, Lilongwe, Malawi
Irving F. Hoffman, UNC Project, Lilongwe, Malawi and University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Maria A. Papathanasopoulos, Department of Molecular Medicine and Haematology, Faculty of Health Sciences, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
Mina Hosseinipour, UNC Project, Lilongwe, Malawi and University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Lesley Scott, Department of Molecular Medicine and Haematology, Faculty of Health Sciences, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
Wendy Stevens, Department of Molecular Medicine and Haematology, Faculty of Health Sciences, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa


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Abstract

Background: Availability and access to the detection of resistance to anti-tuberculosis drug sremains 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 chaintermination 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.


Keywords

Rifampicin resistance; Xpert; DNA sequencing; rpoB mutation.

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doi: 10.1093/jac/dky248