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Free Content inhA promoter mutations: a gateway to extensively drug-resistant tuberculosis in South Africa?

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SETTING: Western Cape and Eastern Cape Provinces, South Africa.

OBJECTIVE: To assess the potential association between the evolution of extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis and mutations in the inhA promoter or the katG gene.

DESIGN: Analysis of the frequency distribution of isoniazid (INH) resistance conferring mutations in a population sample of drug-resistant isolates of M. tuberculosis.

RESULTS: In the Western Cape and Eastern Cape Provinces, the percentage of isolates exhibiting inhA promoter mutations increased significantly from respectively 48.4% and 62.4% in multidrug-resistant tuberculosis (MDR-TB) isolates to 85.5% and 91.9% in XDR isolates. Data from the Western Cape revealed that significantly more XDR-TB isolates showed mutations in the inhA promoter than in katG (85.5% vs. 60.9%, P < 0.01), while the respective proportions were equal for INH-resistant non-MDR-TB isolates (∼30%).

CONCLUSIONS: inhA promoter mutations are strongly associated with XDR-TB in South Africa. We suggest that this is due to the dual resistance to ethionamide and (low-dose) INH conferred by inhA promoter mutations. The use of molecular probe assays such as the GenoType® MTBDRplus assay, which allows the detection of inhA promoter mutations, could enable treatment regimens to be adjusted depending on the pharmacogenetic properties of the mutations detected.
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Keywords: MDR-TB; MTBDRplus; SNP; drug resistance; katG

Document Type: Regular Paper

Affiliations: 1: Biotec Laboratories SA (Pty) Ltd, Cape Town, South Africa 2: National Health Laboratory Service, Greenpoint, Cape Town, South Africa 3: National TB Reference Laboratory, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa 4: Nelson Mandela Bay Municipality, Port Elizabeth, South Africa

Publication date: 2011-03-01

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  • The International Journal of Tuberculosis and Lung Disease publishes articles on all aspects of lung health, including public health-related issues such as training programmes, cost-benefit analysis, legislation, epidemiology, intervention studies and health systems research. The IJTLD is dedicated to the continuing education of physicians and health personnel and the dissemination of information on tuberculosis and lung health world-wide.

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