RESUMO
In order to investigate the role of MBL gene polymorphisms in susceptibility to tuberculosis (TB) we genotyped 487 TB cases and 232 controls. Among African-American individuals, the frequency of B allele was lower among controls than cases (p < 0.01), but we found no differences between cases and controls of white and Hispanic ethnicity.
Assuntos
Predisposição Genética para Doença , Lectina de Ligação a Manose/genética , Polimorfismo Genético , Tuberculose Pulmonar/etnologia , Tuberculose Pulmonar/genética , Adulto , Negro ou Afro-Americano/genética , Idoso , Estudos de Casos e Controles , DNA Bacteriano/análise , Suscetibilidade a Doenças , Feminino , Hispânico ou Latino/genética , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase , Probabilidade , Valores de Referência , Medição de Risco , Estudos de Amostragem , Sensibilidade e Especificidade , Estados Unidos/epidemiologia , População Branca/genéticaRESUMO
Thirty-seven multidrug-resistant and 13 pan-susceptible isolates of Mycobacterium tuberculosis were analysed for the diversity of genotypes associated with known drug-resistance mechanisms. The isolates were obtained from patients attending a university tuberculosis clinic in Monterrey, Mexico. A total of 25 IS6110-RFLP patterns were obtained from the multidrug-resistant tuberculosis (MDR-TB) isolates. Approximately 65% of the MDR-TB isolates were attributed to secondary resistance. Different drug-susceptibility patterns were seen with the clustered isolates. The percentage of isolates resistant to isoniazid (INH), rifampicin (RIF), ethambutol (EMB) and streptomycin (STR) was 100, 97.3, 48.7 and 67.6, respectively. The most common resistance-associated polymorphisms for the four drugs were as follows: INH, Ser315Thr (67.6%) in katG; RIF, Ser450Leu (41.7%) in rpoB; EMB, Met306Ile/Val/Leu (66.7%) in embB; and STR, Lys43Arg (24%) in rpsL. Drug-resistance-associated mutations were similar to changes occurring in isolates from other areas of the world, but unique, previously unreported, mutations in katG (n=5), rpoB (n=1) and rrs (n=3) were also identified.
Assuntos
Antituberculosos/farmacologia , Farmacorresistência Bacteriana Múltipla/genética , Mycobacterium tuberculosis/classificação , Mycobacterium tuberculosis/efeitos dos fármacos , Tuberculose Resistente a Múltiplos Medicamentos/epidemiologia , Proteínas de Bactérias/genética , Elementos de DNA Transponíveis , Genótipo , Humanos , México/epidemiologia , Testes de Sensibilidade Microbiana , Mutação , Mycobacterium tuberculosis/genética , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , Análise de Sequência de DNA , Tuberculose Resistente a Múltiplos Medicamentos/microbiologiaRESUMO
Isoniazid (INH) is a central component of drug regimens used worldwide to treat tuberculosis. Previous studies have identified resistance-associated mutations in katG, inhA, kasA, ndh, and the oxyR-ahpC intergenic region. DNA microarray-based experiments have shown that INH induces several genes in Mycobacterium tuberculosis that encode proteins physiologically relevant to the drug's mode of action. To gain further insight into the molecular genetic basis of INH resistance, 20 genes implicated in INH resistance were sequenced for INH resistance-associated mutations. Thirty-eight INH-monoresistant clinical isolates and 86 INH-susceptible isolates of M. tuberculosis were obtained from the Texas Department of Health and the Houston Tuberculosis Initiative. Epidemiologic independence was established for all isolates by IS6110 restriction fragment length polymorphism analysis. Susceptible isolates were matched with resistant isolates by molecular genetic group and IS6110 profiles. Spoligotyping was done with isolates with five or fewer IS6110 copies. A major genetic group was established on the basis of the polymorphisms in katG codon 463 and gyrA codon 95. MICs were determined by the E-test. Semiquantitative catalase assays were performed with isolates with mutations in the katG gene. When the 20 genes were sequenced, it was found that 17 (44.7%) INH-resistant isolates had a single-locus, resistance-associated mutation in the katG, mabA, or Rv1772 gene. Seventeen (44.7%) INH-resistant isolates had resistance-associated mutations in two or more genes, and 76% of all INH-resistant isolates had a mutation in the katG gene. Mutations were also identified in the fadE24, Rv1592c, Rv1772, Rv0340, and iniBAC genes, recently shown by DNA-based microarray experiments to be upregulated in response to INH. In general, the MICs were higher for isolates with mutations in katG and the isolates had reduced catalase activities. The results show that a variety of single nucleotide polymorphisms in multiple genes are found exclusively in INH-resistant clinical isolates. These genes either are involved in mycolic acid biosynthesis or are overexpressed as a response to the buildup or cellular toxicity of INH.
