Bases moleculares da multiresistência a drogas em <i>Mycobacterium tuberculosis</i>

• Autor(a) principal: Freitas, Flávia Alvim Dutra de
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/16289
• topic: Tuberculosis; Rifampin; Isoniazid; Multidrug resistance; Tuberculose; Rifampicina; Isoniazida; Multirresistencia; Mycobacterium tuberculosis; Drogas Resistência; Tuberculose Tratamento; Mutagênese; Rifampicina; Isoniazida; Pirazinamida; CNPQ::CIENCIAS BIOLOGICAS::BIOQUIMICA::BIOLOGIA MOLECULAR

Tuberculosis (Tb) is the main cause of death in the world due to a infectious pathogenic agent. The standard treatment is chemotherapy: rifampicin (RMP), isoniazid (INH), and pyrazinamide (PZA). One of the most serious global problems is the increase in the occurrence of multidrug resistant <i>M. tuberculosis</i> (MTb) strains, resistant to, at least, INH and RMP. Resistance to INH and RMP generally occurs by gene mutations in the KatG and rpoB genes, respectively. There are two objectives in this thesis: 1- To analyze the type and frequencies of mutations in two different regions of the katG gene; 2- To determine the type and frequency of rpoB gene mutations. Two regions of the KatG gene and one of the rpoB gene were amplified by PCR, and sequenced to identify the mutations. For the analysis of the katG gene 101 strains were used. Among them, 4 were sensitive and showed no mutation (controls). Among the 97 remaining, in the first sequenced region of the katG gene, no mutations occurred in 67. Thirty cases had 33 nucleotide deletions, with 24 deletions at codon 4 (24.7%), which characterized a new allele. In region 2, 16 strains had no mutations - seven were associated with a lack of mutations in region 1. There were also 83 mutations, 73 in codon 315 (75.3%). Seven INH-resistant strains showed no mutations in any of the two regions analyzed. Mutations in region 2 allowed the diagnosis of INH resistance in 79 strains or 81.4%. Nine strains which showed no mutations in region 2 had mutations in region 1. This means that the analysis of this region allowed the increase in INH resistance diagnosis for 88 strains (90.7%), increasing the positive rate in 9.3%. In seven cases, there were no mutations associated with resistance in any of the regions. In the rpoB analysis 120 MTb strains were used. No mutations were found in 13 RMP resistant isolates. The codon with the highest mutation frequency was 531 (45.6%), followed by 526 (26%) and 516 (12.5%). In other eleven codons, a total of 18 mutations were found (15.2%), mainly at codons 511 (3.4%) and 513 (3.4%). None of the RMP sensitive isolates showed any mutations. In the State of Rio de Janeiro, the most frequent mutations were: 516 (5%), 526 (2.5%) and 531 (21.2%). Within the other states, the most frequent mutations were: 516 (2.5%), 526 (11%) and 531 (19.4%). The frequency of mutations at codons 516, 526 and 531 from the Rio de Janeiro isolates was compared with those found in other states. When Rio de Janeiro was removed from the analysis, the frequency of mutations at codons 531 and 526 for the other 15 states was similar. The statistical analysis shows that this data is significant (p = 0.002). However, when all states were analyzed together, the codon 531 is again the most frequently mutated. The analysis of the rpoB gene diagnosed RMP resistance in 89.17% of the strains. Our results confirm that, in Brazil, mutations in the RRDR of the rpoB gene are good predictors of RMP resistance.