Determinação do nível de resistência a isoniazida em cepas de Mycobacterium tuberculosis e correlação com mutações nos genes que conferem resistência a este fármaco: katG e inhA / Determination of the level of resistance to isoniazid in strains of Mycobacterium tuberculosis and correlation with mutations in genes that confer resistance to this drug: katG and inhA

RESUMO

A tuberculose (TB) resistente aos fármacos é um problema mundial. As mutações mais frequentes associadas à resistência à isoniazida em Mycobacterium tuberculosis ocorrem no códon 315 do gene katG, causando níveis moderados a altos de resistência, e na região promotora do gene inhA, associadas a baixos níveis de resistência. Mutações no gene rpoB associam-se à resistência à rifampicina. Este estudo analisou mutações nos genes katG, inhA e rpoB e níveis fenotípicos de resistência à isoniazida em isolados de M. tuberculosis de pacientes com TB resistente do estado de São Paulo, no período de outubro/2008 a março/2009 e no ano de 2016. Dos 374 isolados analisados, 165 (44%) eram monorresistentes à isoniazida, 47 (13%) polirresistentes (resistentes à isoniazida+fármaco(s) de 1ª linha exceto rifampicina), 122 (33%) multirresistentes (MR), 24 (6%) pré-extensivamente resistentes (pré-XDR) e 16 (4%) XDR. Entre os isolados com a mutação Ser315Thr no katG, 99,4% apresentaram resistência intermediária ou alta à isoniazida, enquanto 73,7% dos isolados com a mutação C-15T no inhA apresentaram baixa resistência. Dos isolados com mutações no katG e inhA, 66,6% mostraram resistência alta e 32,4% resistência intermediária. Observou-se que 58,8% dos isolados tipados estavam em cluster e 43,7% deles pertenciam...(AU)

ABSTRACT

Drug-resistant tuberculosis (TB) is a problem worldwide. The most frequent mutations associated with isoniazid resistance in Mycobacterium tuberculosis isolates occur in codon 315 of the katG gene, which have been associated with moderate- to high-levels of resistance, and in the promoter region of the inhA gene, causing low-level isoniazid resistance. In its turn, the rpoB gene is associated with resistance to rifampicin. This study analyzed mutations in katG, inhA and rpoB genes and phenotypic levels of isoniazid resistance in M. tuberculosis isolates from drug-resistant TB patients from the state of São Paulo, in the period of October 2008 to March 2009 and during the year of 2016. Of the 374 M. tuberculosis isolates analyzed 165 (44%) were monoresistant to isoniazid, 47 (13%) polydrug-resistant (resistant to isoniazid+1st line drug(s) except rifampicin), 122 (33%) multidrug-resistant (MDR), 24 (6%) pre-extensively drug-resistant (pre-XDR) and 16 (4%) XDR. Among isolates with the katG Ser315Thr mutation, 99.4% had intermediate or high-level isoniazid resistance, while 73.7% of the isolates with the inhA C15T mutation had low-level resistance. Among isolates with mutations in katG and inhA, 66.6% had high-level resistance and 32.4% had intermediate resistance. It was observed that 58.8% of the isolates submitted to typing were clustered, and 43.7% of them belonged to the five most prevalent clusters SP5, SP2c, SP12, SP5ac and SP1i. Isolates with katG 315 mutations were more frequently clustered when compared to isolates with other katG mutations or with no mutations (p= 0.002 and 0.01, respectively). Isolates with the inhA C-15T mutation were more frequently clustered when compared to isolates with katG 315 mutations (p= 0.006). Statistically significant differences were found between cure rates of isoniazidmonoresistant TB patients and MDR-TB patients (63.4% vs 47.1%, p= 0.02), as well as between isoniazid-monoresistant TB patients and XDR-TB patients (63.4% vs 12.5%, p= 0.01). Patients with polydrug-resistant TB also had higher cure rates than patients with MDR-TB (70% vs 47.1%, p= 0.02) and XDR-TB (12.5%, p= 0.004). The present study showed that katG mutations are associated with higher levels of isoniazid resistance and inhA mutations are found in isolates with lower resistance levels. In addition, drugresistant TB was transmitted among patients from the state of São Paulo, whose cure rates were relatively low. (AU)