RESUMEN
Tuberculosis patients taking second line drugs such as ethionamide (ETH) have often experienced previous treatment failure and usually have a complex history of disease and treatment that can span decades. Mutations in the ETH activating enzyme, EthA, confer resistance through undescribed mechanisms. To explore the impact of EthA mutations on ETH resistance, data from a total of 160 ETHR isolates was analysed. The most frequently mutated positions are within regions that display sequence conservation with the active site of OTEMO, another FAD-containing NADH-binding Baeyer-Villiger monooxygenase (BVMO), or with the sugar binding site of galectin-4N. Additionally, to look at a possible role of EthR on ETH resistance we purified an EthR mutant identified in a clinical isolate, F110L, and found it to bind the ethA-ethR intergenic region with higher affinity than the wild type regulator in gel shift assays. The ability of cyclic di-GMP to enhance DNA binding is maintained in the EthR mutant. To our knowledge, this is the first ETH resistance study that combines sequence and resistance data of clinical isolates with functional and structural information.
Asunto(s)
Antituberculosos/uso terapéutico , ADN Bacteriano/genética , Farmacorresistencia Bacteriana/genética , Etionamida/uso terapéutico , Sitios Genéticos , Mycobacterium tuberculosis/genética , Tuberculosis/microbiología , Sitios de Unión , ADN Bacteriano/aislamiento & purificación , Genotipo , Humanos , Mutación , Mycobacterium tuberculosis/efectos de los fármacos , Mycobacterium tuberculosis/enzimología , Mycobacterium tuberculosis/aislamiento & purificación , Oxidorreductasas/genética , Fenotipo , Unión Proteica , Conformación Proteica , Proteínas Represoras/genética , Relación Estructura-Actividad , Tuberculosis/diagnóstico , Tuberculosis/tratamiento farmacológicoRESUMEN
Tuberculosis is a major public health concern, and diagnostic strategies applied to animal populations are scarce. As part of ongoing efforts to control tuberculosis dissemination at our animal facility, two non-human primates (NHP, Saimiri sciureus) presenting cutaneous lesions were examined for mycobacterial infection. Both animals tested positive for acid-fast bacilli and Mycobacterium tuberculosis using a molecular assay (IS6110 PCR). Animals were euthanized and several samples were tested for M. tuberculosis using the Xpert MTB/RIF assay. Many samples were positive for M. tuberculosis and rifampicin resistance, and some produced mycobacterial growth. Oral swabs from cage mates were then tested with Xpert MTB/RIF, and the majority tested positive for M. tuberculosis and rifampicin resistance, and produced growth in culture. To our knowledge, this is the first report of multidrug-resistant mycobacterial infection in NHP. Additionally, our data shows that the Xpert MTB/RIF assay can be useful as a screening tool for tuberculosis infection in NHP.