Abstract
BackgroundThere are limited data about the epidemiology and treatment-related outcomes associated with capreomycin resistance in patients with XDR-TB. Capreomycin achieves high serum concentrations relative to MIC but whether capreomycin has therapeutic benefit despite microbiological resistance remains unclear.MethodsWe reviewed the susceptibility profiles and outcomes associated with capreomycin usage in patients diagnosed with XDR-TB between August 2002 and October 2012 in two provinces of South Africa. Patients whose isolates were genotypically tested for capreomycin resistance were included in the analysis.ResultsOf 178 XDR-TB patients 41% were HIV-infected. 87% (154/178) isolates contained a capreomycin resistance-conferring mutation [80% (143/178) rrs A1401G and 6% (11/178) were heteroresistant (containing both the rrs A1401G mutation and wild-type sequences)]. Previous MDR-TB treatment, prior usage of kanamycin, or strain type was not associated with capreomycin resistance. 92% (163/178) of XDR-TB patients were empirically treated with capreomycin. Capreomycin resistance decreased the odds of sputum culture conversion. In capreomycin sensitive and resistant persons combined weight at diagnosis was the only independent predictor for survival (p=<0.001). By contrast, HIV status and use of co-amoxicillin/clavulanic acid were independent predictors of mortality (p=<0.05). Capreomycin usage was not associated with survival or culture conversion when the analysis was restricted to those whose isolates were resistant to capreomycin.ConclusionIn South Africa the frequency of capreomycin conferring mutations was extremely high in XDR-TB isolates. In those with capreomycin resistance there appeared to be no therapeutic benefit of using capreomycin. These data inform susceptibility testing and the design of treatment regimens for XDR-TB in TB endemic settings.
Highlights
Multi-drug resistant tuberculosis (MDR-TB) is a burgeoning problem worldwide with an estimated ~480 000 cases recorded globally in 2014 [1]
Previous MDR-TB treatment, prior usage of kanamycin, or strain type was not associated with capreomycin resistance. 92% (163/178) of XDR-TB patients were empirically treated with capreomycin
In South Africa the frequency of capreomycin conferring mutations was extremely high in XDR-TB isolates
Summary
Multi-drug resistant tuberculosis (MDR-TB) is a burgeoning problem worldwide with an estimated ~480 000 cases recorded globally in 2014 [1]. Patients with XDR-TB are resistant to four potent anti-TB drugs (rifampicin, isoniazid, fluoroquinolones and aminoglycosides) and in South Africa, resistance to the latter two drugs is mostly acquired (i.e. a high proportion of cases have been infected with a circulating MDR-TB strain). This in part is due to a weakened MDR-TB regimen because of the unrecognized high level of ethionamide resistance [13]. Defining the context-specific risk-benefit ratio of capreomycin is critical Such data inform advocacy efforts to accelerate the development of new anti-TB drugs and trial of immunotherapeutic options in patients with XDR-TB. Capreomycin achieves high serum concentrations relative to MIC but whether capreomycin has therapeutic benefit despite microbiological resistance remains unclear
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