Ethambutol (EMB) resistance can evolve through a multistep process, and mutations in the ubiA (Rv3806c) gene appear to be responsible for high-level EMB resistance in Mycobacterium tuberculosis. We evaluated the prevalence of ubiA and embB (Rv3795) mutations in EMB-resistant strains originating from Africa and South Korea. No differences in embB mutation frequencies were observed between strains from both origins. However, ubiA mutations were present in 45.5% 6.5% of the African EMB-resistant isolates but in only 9.5% 1.5% of the South Korean EMB-resistant isolates. The ubiA mutations associated with EMB resistance were localized to regions encoding the transmembrane domains of the protein, whereas the embB mutations were localized to regions encoding the extramembrane domains. Larger studies are needed to investigate the causes of increased ubiA mutations as a pathway to high-level EMB resistance in African countries, such as extended EMB usage during tuberculosis treatment.

To improve tuberculosis (TB) diagnosis, many national TB programmes have committed to deploying Xpert® MTB/RIF. Implementation of this relatively new technology has suffered from a lack of comprehensive technical assistance, however, including the formulation of policies and plans to address operational issues. While providing technical assistance, we observed numerous operational challenges in the implementation and scale-up of Xpert in five sub-Saharan African countries: low coverage, poor laboratory infrastructure, limited access, poor linkages to treatment, inadequate data on outcomes, problems with specimen transport, diagnostic algorithms that are not aligned with updated World Health Organization recommendations on target patient groups and financing challenges. We recommend better country preparedness and training, laboratory information and quality systems, supply management and referral mechanisms.

We set out to evaluate the variation in prevalence of drug resistant tuberculosis (DR-TB) and its determinants across sub-Saharan African (SSA) countries--excluding South Africa--among new and previously treated TB patients. A search of PubMed, EMBASE, Cochrane and bibliographies of DR-TB studies yielded 726 studies published between 2003 and 2013, of which 27 articles fulfilled the inclusion criteria. Studies reported drug susceptibility testing results for a total of 13,465 new and 1,776 previously treated TB patients. The pooled estimate of any DR-TB prevalence among the new cases was 12.6%, while for MDR-TB this was 1.5%. Among previously treated patients, these were 27.2% and 10.3%, respectively. DR-TB (any and MDR-TB) did not vary significantly with respect to study characteristics. The reported prevalence of DR-TB in SSA is low compared to WHO estimates. MDR-TB in this region does not seem to be driven by the high HIV prevalence rates.

As HIV care services continue to scale-up in sub-Saharan Africa, adequate tuberculosis diagnostic capacity is vital to reduce mortality among HIV-infected persons.

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