RESUMO
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RESUMO
The rpoB gene encodes the ß subunit of RNA polymerase holoenzyme in Mycobacterium leprae (M. leprae). Missense mutations in the rpoB gene were identified as etiological factors for rifampin resistance in leprosy. In the present study, we identified mutations corresponding to rifampin resistance in relapsed leprosy cases from three hospitals in southern India which treat leprosy patients. DNA was extracted from skin biopsies of 35 relapse/multidrug therapy non-respondent leprosy cases, and PCR was performed to amplify the 276 bp rifampin resistance-determining region of the rpoB gene. PCR products were sequenced, and mutations were identified in four out of the 35 cases at codon positions D441Y, D441V, S437L and H476R. The structural and functional effects of these mutations were assessed in the context of three-dimensional comparative models of wild-type and mutant M. leprae RNA polymerase holoenzyme (RNAP), based on the recently solved crystal structures of RNAP of Mycobacterium tuberculosis, containing a synthetic nucleic acid scaffold and rifampin. The resistance mutations were observed to alter the hydrogen-bonding and hydrophobic interactions of rifampin and the 5' ribonucleotide of the growing RNA transcript. This study demonstrates that rifampin-resistant strains of M. leprae among leprosy patients in southern India are likely to arise from mutations that affect the drug-binding site and stability of RNAP.
Assuntos
Proteínas de Bactérias/genética , RNA Polimerases Dirigidas por DNA/genética , Farmacorresistência Bacteriana/genética , Hansenostáticos/farmacologia , Hanseníase/tratamento farmacológico , Mycobacterium leprae/genética , Rifampina/farmacologia , Adolescente , Adulto , DNA Bacteriano/genética , Feminino , Humanos , Índia , Hansenostáticos/uso terapêutico , Hanseníase/microbiologia , Masculino , Testes de Sensibilidade Microbiana , Pessoa de Meia-Idade , Mutação , Mycobacterium leprae/efeitos dos fármacos , Mycobacterium leprae/isolamento & purificação , Ligação Proteica/genética , Estabilidade Proteica/efeitos dos fármacos , Recidiva , Rifampina/uso terapêutico , Análise de Sequência de DNA , Relação Estrutura-Atividade , Resultado do Tratamento , Adulto JovemRESUMO
A 26-year-old man presented with swelling of his face and nose of three months duration. He had multiple hyperpigmented, hyperkeratotic plaques over the swelling, of one-month duration and an erythematous indurated plaque below the left nostril for two weeks. Based on a biopsy taken from the antral mass with special stain for fungus, he was treated as fungal sinusitis with intravenous amphotericin-B, but the lesion did not regress. Later a skin biopsy from the indurated lesion showed moderately differentiated squamous cell carcinoma. A diagnosis of sinonasal carcinoma was made and chemotherapy was started.