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Revista chilena de infectología

Print version ISSN 0716-1018


ROMAY, Zolay et al. Detection of S315T mutation in the katg gene as a strategy for identification of isoniazid-resistant Mycobacterium tuberculosis in a reference laboratory. Rev. chil. infectol. [online]. 2012, vol.29, n.6, pp.607-613. ISSN 0716-1018.

Introduction: The emergence of strains of Mycobacterium tuberculosis resistant to drugs is a public health problem. Aim: To characterize the resistance to isoniazid (INH) in M. tuberculosis. Methods: Phenotypic and genotypic methods were used to determine the contribution of mutations at 315 codon of katG gene to the phe-notypic expression of resistance. The analysis of susceptibility to antibiotics was performed by the proportional method of Canetti and nitrate reductase method.Genotypic analysis of INH resistance was performed by PCR-RFLP. Results: 193 strains of M. tuberculosis from patients with respiratory symptoms were analyzed. Nineteen (9.8%) strains resistant to INH were identified, of which 12 (63.2%) showed resistance to other drugs. Genotypic analysis allowed to detect the mutation S315T in the katG gene in 15 of 17 strains phenotypically resistant to INH, showing a sensitivity of 88.24%, 100% specificity, 100% positive predictive value, 92% negative predictive value and high concordance with phenotypic methods (kappa = 0.85 (p < 0.01). Conclusion: The S315T mutation in the katG gene is the predominant mechanism of INH resistance in our circulating strains. This feature could be used as a rapid diagnostic tool with potential to detect at least 88% of isoniazid resistant strains, with great impact on the therapeutic management of patients.

Keywords : Mycobacterium tuberculosis; resistance to isoniazid; MDR-TB; nitrate reductase; katGS315T.

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