RESUMEN
Genomic-based surveillance on the occurrence of drug resistance and its transmission dynamics has emerged as a powerful tool for the control of tuberculosis (TB). A whole-genome sequencing approach, phenotypic testing and clinical-epidemiological investigation were used to undertake a retrospective population-based study on drug-resistant (DR)-TB in Rio Grande do Sul, the largest state in Southern Brazil. The analysis included 305 resistant Mycobacterium tuberculosis strains sampled statewide from 2011 to 2014, and covered 75.7% of all DR-TB cases identified in this period. Lineage 4 was found to be predominant (99.3%), with high sublineage-level diversity composed mainly of 4.3.4.2 [Latin American and Mediterranean (LAM)/RD174], 4.3.3 (LAM/RD115) and 4.1.2.1 (Haarlem/RD182) sublineages. Genomic diversity was also reflected in resistance of the variants to first-line drugs. A large number of distinct resistance-conferring mutations, including variants that have not been reported previously in any other setting worldwide, and 22 isoniazid-monoresistant strains with mutations described as disputed in the rpoB gene but causing rifampicin resistance generally missed by automated phenotypic tests as BACTEC MGIT. Using a cut-off of five single nucleotide polymorphisms, the estimated recent transmission rate was 55.1%, with 168 strains grouped into 28 genomic clusters. The most worrying fact concerns multi-drug-resistant (MDR) strains, of which 73.4% were clustered. Different resistance profiles and acquisition of novel mutations intraclusters revealed important amplification of resistance in the region. This study described the diversity of M. tuberculosis strains, the basis of drug resistance, and ongoing transmission dynamics across the largest state in Southern Brazil, stressing the urgent need for MDR-TB transmission control state-wide.
Asunto(s)
Antibióticos Antituberculosos/uso terapéutico , Proteínas Bacterianas/genética , ARN Polimerasas Dirigidas por ADN/genética , Farmacorresistencia Bacteriana Múltiple/genética , Mycobacterium tuberculosis/efectos de los fármacos , Tuberculosis Resistente a Múltiples Medicamentos/genética , Tuberculosis Resistente a Múltiples Medicamentos/transmisión , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Antituberculosos/uso terapéutico , Brasil/epidemiología , Perfilación de la Expresión Génica , Genoma Bacteriano/genética , Humanos , Isoniazida/uso terapéutico , Pruebas de Sensibilidad Microbiana , Persona de Mediana Edad , Mycobacterium tuberculosis/genética , Polimorfismo de Nucleótido Simple/genética , Estudios Retrospectivos , Rifampin/uso terapéutico , Tuberculosis Resistente a Múltiples Medicamentos/epidemiología , Secuenciación Completa del Genoma , Adulto JovenRESUMEN
PURPOSE: The establishment of candidate genetic determinants associated with tuberculosis (TB) is a challenge, considering the divergent frequencies among populations. The objective of this study was to evaluate the association between MIF - 794 CATT 5-8 polymorphism and susceptibility to TB. METHODS: Case-control study. Patients > 18 years, with pulmonary TB were included. The control group consisted of blood donors and household contacts, not relatives, healthy and > 18 years. MIF - 794 CATT 5-8 were genotyped using sequencing of PCR and capillary electrophoresis. RESULTS: 126 patients and 119 controls were included. The genotype 5/5 was more frequent among cases (15.1%) than in controls (5.9%) (p = 0.019). Cases had more frequently the allele 5 (29.4%) as compared with controls (19.3%) (p = 0.010). Prevalence of 7/X + 8/X genotypes was not different between cases and controls (p = 0.821). There was no difference between patients with alleles 7 and 8 and those with alleles 5 and 6 (p = 0.608). CONCLUSIONS: The genotype 5/5 and the allele 5 of MIF - 794 CATT 5-8 were more frequent among TB patients than in controls.
Asunto(s)
Predisposición Genética a la Enfermedad , Factores Inhibidores de la Migración de Macrófagos , Tuberculosis , Estudios de Casos y Controles , Frecuencia de los Genes , Genotipo , Humanos , Oxidorreductasas Intramoleculares , Factores Inhibidores de la Migración de Macrófagos/genética , Repeticiones de Microsatélite , Polimorfismo de Nucleótido Simple , Tuberculosis/genéticaRESUMEN
PURPOSE: The establishment of candidate genes associated with susceptibility to TB is a challenge especially due to divergent frequencies among different populations. The objective of this study was to evaluate the association between macrophage migration inhibitory factor (MIF) -173 G>C single nucleotide polymorphism (SNP) and susceptibility to pulmonary TB in a population of southern Brazil. METHODS: Case-control study. Patients > 18 years old, diagnosed with pulmonary TB were included. The control group consisted of blood donors and household contacts, not relatives, healthy and > 18 years old. MIF -173 G>C SNPs were genotyped using real-time PCR using a TaqMan SNP Genotyping assay. RESULTS: 174 patients and 166 controls were included. There were no statistically significant differences between cases and controls regarding genotype prevalence (p>0.05). Comparing patients with normal genotype (GG) with those with at least one C allele, there was also no statistically significant difference (p = 0.135). Also, there was no statistically significant difference comparing the homozygous for the mutation (CC) with the other patients (GG and CG) (p = 0.864). CONCLUSIONS: We did not find association between MIF -173 G>C polymorphism and susceptibility to pulmonary TB.
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Oxidorreductasas Intramoleculares/genética , Factores Inhibidores de la Migración de Macrófagos/genética , Polimorfismo de Nucleótido Simple , Tuberculosis Pulmonar/genética , Adolescente , Adulto , Anciano , Brasil , Estudios de Casos y Controles , Femenino , Humanos , Masculino , Persona de Mediana Edad , Tuberculosis Pulmonar/patologíaRESUMEN
Drug-resistant tuberculosis (DR-TB) is major problem in the fight against TB. Multidrug resistant (MDR) TB patients have a reduced treatment success rates and for, extensively drug-resistant (XDR) TB the cure rate does not exceed 25% in many countries. To evaluate the pre-XDR-TB and XDR-TB prevalence and transmission in Rio Grande do Sul State, in southern Brazil, we performed a retrospective WGS-based analysis of 87 MDR-TB cases, aiming to identify resistance-conferring mutations and its phylogenetic distinctiveness. Using a five SNP threshold for genomic clustering, 60 strains were genomically linked within 10 clusters, including 14 likely transmission events identified by retrospective conventional epidemiological investigation. Moreover, five likely transmission events involved 17 patients deprived of liberty in the same prison establishment. Mutations associated with isoniazid and rifampicin resistance were identified respectively in 97.70% and 98.85% of MDR M.tb strains, more frequently in katG and rpoB genes. In total, we identified eight (9.19%) pre-XDR and four (4.59%) XDR M.tb strains. Resistance to ofloxacin was observed in seven (8.04%) strains, all of them presenting resistance-conferring mutations. Phenotypic resistance from capreomycin and kanamycin was found in seven (8.04%) and four (4.59%) strains respectively, but no classic mutations associated with resistance to these drugs was identified. The results put in evidence a scenario involving multiple phylogenetically distinctive clades associated with pre-XDR and XDR-TB in the largest state of southern Brazil, while stressing the potential of using WGS to predict anti-TB drug resistance and need to halt MDR-TB transmission in the region.
Asunto(s)
Mycobacterium tuberculosis/efectos de los fármacos , Mycobacterium tuberculosis/genética , Tuberculosis Resistente a Múltiples Medicamentos/epidemiología , Tuberculosis Resistente a Múltiples Medicamentos/microbiología , Adulto , Antituberculosos/farmacología , Brasil/epidemiología , Farmacorresistencia Bacteriana Múltiple/genética , Tuberculosis Extensivamente Resistente a Drogas/epidemiología , Tuberculosis Extensivamente Resistente a Drogas/microbiología , Femenino , Variación Genética , Humanos , Masculino , Pruebas de Sensibilidad Microbiana , Persona de Mediana Edad , Repeticiones de Minisatélite , Mutación , Mycobacterium tuberculosis/aislamiento & purificación , Filogenia , Polimorfismo de Nucleótido Simple , Tuberculosis Resistente a Múltiples Medicamentos/transmisión , Secuenciación Completa del GenomaRESUMEN
INTRODUCTION: Induced sputum (IS) is an alternative method of obtaining sputum, but IS smears are frequently negative. Culture is more time consuming in its results, and less useful to guide the diagnosis. Polymerase chain reaction (PCR) is the most common methodology for rapid diagnosis of tuberculosis (TB), and few studies evaluated its role in IS samples. OBJECTIVES: The objective of this study is to determine the diagnostic yield of PCR for TB compared with culture in IS samples. MATERIALS AND METHODS: Prospective study. Inpatients and outpatients of >18 years with respiratory symptoms suggestive of PTB were invited to participate. The subjects were interviewed using a standardized questionnaire, and collected IS. Three samples were obtained for AFB smear and culture. A fourth sample was obtained for PCR test. RESULTS: A total of 116 IS samples were evaluated. The sensitivity, specificity, positive predictive value and negative predictive values of PCR were 95.2%, 48.4%, 29.0% and 97.9%, respectively. The area under the receiver operating characteristic curve was .72 for the PCR test (P < .0001). CONCLUSIONS: Although the PCR specificity could be underestimated, if we consider PCR to be more sensitive than the culture method used, we believed that these PCR-positive tests mean false positives. The results of PCR should always be interpreted carefully in conjunction with clinical information.
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Reacción en Cadena de la Polimerasa/métodos , Esputo/microbiología , Tuberculosis Pulmonar/diagnóstico , Tuberculosis Pulmonar/microbiología , Adulto , Anciano , Brasil/epidemiología , Comorbilidad , Cultura , Reacciones Falso Positivas , Femenino , Humanos , Masculino , Persona de Mediana Edad , Mycobacterium tuberculosis/genética , Valor Predictivo de las Pruebas , Estudios Prospectivos , Sensibilidad y EspecificidadRESUMEN
BACKGROUND: To cope with the emergence of multidrug-resistant tuberculosis (MDR-TB), new molecular methods that can routinely be used to screen for a wide range of drug resistance related genetic markers in the Mycobacterium tuberculosis genome are urgently needed. OBJECTIVE: To evaluate the performance of multiplex ligaton-dependent probe amplification (MLPA) against Genotype® MTBDRplus to detect resistance to isoniazid (INHr) and rifampicin (RIFr). METHOD: 96 culture isolates characterised for identification, drug susceptibility testing (DST) and sequencing of rpoB, katG, and inhA genes were evaluated by the MLPA and Genotype®MTBDRplus assays. RESULTS: With sequencing as a reference standard, sensitivity (SE) to detect INHr was 92.8% and 85.7%, and specificity (SP) was 100% and 97.5%, for MLPA and Genotype®MTBDRplus, respectively. In relation to RIFr, SE was 87.5% and 100%, and SP was 100% and 98.8%, respectively. Kappa value was identical between Genotype®MTBDRplus and MLPA compared with the standard DST and sequencing for detection of INHr [0.83 (0.75-0.91)] and RIFr [0.93 (0.88-0.98)]. CONCLUSION: Compared to Genotype®MTBDRplus, MLPA showed similar sensitivity to detect INH and RIF resistance. The results obtained by the MLPA and Genotype®MTBDRplus assays indicate that both molecular tests can be used for the rapid detection of drug-resistant TB with high accuracy. MLPA has the added value of providing information on the circulating M. tuberculosis lineages.
Asunto(s)
Antibióticos Antituberculosos/farmacología , Farmacorresistencia Bacteriana Múltiple/genética , Isoniazida/farmacología , Mycobacterium tuberculosis/efectos de los fármacos , Rifampin/farmacología , Tuberculosis Resistente a Múltiples Medicamentos/microbiología , ADN Bacteriano/genética , Farmacorresistencia Bacteriana Múltiple/efectos de los fármacos , Genotipo , Humanos , Pruebas de Sensibilidad Microbiana , Reacción en Cadena de la Polimerasa Multiplex , Mycobacterium tuberculosis/genética , FenotipoRESUMEN
BACKGROUND To cope with the emergence of multidrug-resistant tuberculosis (MDR-TB), new molecular methods that can routinely be used to screen for a wide range of drug resistance related genetic markers in the Mycobacterium tuberculosis genome are urgently needed. OBJECTIVE To evaluate the performance of multiplex ligaton-dependent probe amplification (MLPA) against Genotype® MTBDRplus to detect resistance to isoniazid (INHr) and rifampicin (RIFr). METHOD 96 culture isolates characterised for identification, drug susceptibility testing (DST) and sequencing of rpoB, katG, and inhA genes were evaluated by the MLPA and Genotype®MTBDRplus assays. RESULTS With sequencing as a reference standard, sensitivity (SE) to detect INHr was 92.8% and 85.7%, and specificity (SP) was 100% and 97.5%, for MLPA and Genotype®MTBDRplus, respectively. In relation to RIFr, SE was 87.5% and 100%, and SP was 100% and 98.8%, respectively. Kappa value was identical between Genotype®MTBDRplus and MLPA compared with the standard DST and sequencing for detection of INHr [0.83 (0.75-0.91)] and RIFr [0.93 (0.88-0.98)]. CONCLUSION Compared to Genotype®MTBDRplus, MLPA showed similar sensitivity to detect INH and RIF resistance. The results obtained by the MLPA and Genotype®MTBDRplus assays indicate that both molecular tests can be used for the rapid detection of drug-resistant TB with high accuracy. MLPA has the added value of providing information on the circulating M. tuberculosis lineages.
Asunto(s)
Humanos , ADN Bacteriano/genética , Tuberculosis Resistente a Múltiples Medicamentos/microbiología , Farmacorresistencia Bacteriana Múltiple/efectos de los fármacos , Farmacorresistencia Bacteriana Múltiple/genética , Isoniazida/farmacología , Antibióticos Antituberculosos/farmacología , Mycobacterium tuberculosis/efectos de los fármacos , Mycobacterium tuberculosis/genética , Resistencia a Medicamentos , AntibacterianosRESUMEN
BACKGROUND: In high tuberculosis (TB) burden countries, there are few data on the performance of new molecular commercialised assays developed locally. OBJECTIVE: To evaluate the performance of a new molecular commercialised assay for TB diagnosis (Detect-TB) in three laboratories. METHODS: A total of 302 sputum samples from an equal number of patients with presumptive diagnosis of pulmonary tuberculosis (PTB) were submitted for routine smear microscopy, culture, and Detect-TB assay at three different sites in Brazil (the cities of Caxias do Sul, São Paulo and Canoas). FINDINGS: Seventy four (24.7%) TB cases were diagnosed (65 bacteriologically confirmed). When compared to smear microscopy/culture results, the overall sensitivity and specificity of Detect-TB assay was 84.6% (CI 95%; 73.7-91.6) and 93.1% (CI 95%; 89.1-95.8), respectively. When compared to bacteriological and clinical diagnostic criteria, the sensitivity and specificity of Detect-TB assay was 74.3% (CI 95%; 63.3-82.9) and 92.9% (CI 95%; 88.7-95.6), respectively. Among the three sites - Caxias do Sul, São Paulo and Canoas - the sensitivity and specificity were respectively 94.7% and 97.8%; 71.4% and 93.9%, 82.1% and 88.9%. MAIN CONCLUSIONS: These findings suggest that the Detect-TB assay could be applied routinely in reference laboratories across different regions in Brazil.
Asunto(s)
Mycobacterium tuberculosis/genética , Esputo/microbiología , Tuberculosis Pulmonar/diagnóstico , Brasil , ADN Bacteriano , Reacciones Falso Negativas , Reacciones Falso Positivas , Humanos , Mycobacterium tuberculosis/aislamiento & purificación , Sensibilidad y EspecificidadRESUMEN
BACKGROUND In high tuberculosis (TB) burden countries, there are few data on the performance of new molecular commercialised assays developed locally. OBJECTIVE To evaluate the performance of a new molecular commercialised assay for TB diagnosis (Detect-TB) in three laboratories. METHODS A total of 302 sputum samples from an equal number of patients with presumptive diagnosis of pulmonary tuberculosis (PTB) were submitted for routine smear microscopy, culture, and Detect-TB assay at three different sites in Brazil (the cities of Caxias do Sul, São Paulo and Canoas). FINDINGS Seventy four (24.7%) TB cases were diagnosed (65 bacteriologically confirmed). When compared to smear microscopy/culture results, the overall sensitivity and specificity of Detect-TB assay was 84.6% (CI 95%; 73.7-91.6) and 93.1% (CI 95%; 89.1-95.8), respectively. When compared to bacteriological and clinical diagnostic criteria, the sensitivity and specificity of Detect-TB assay was 74.3% (CI 95%; 63.3-82.9) and 92.9% (CI 95%; 88.7-95.6), respectively. Among the three sites - Caxias do Sul, São Paulo and Canoas - the sensitivity and specificity were respectively 94.7% and 97.8%; 71.4% and 93.9%, 82.1% and 88.9%. MAIN CONCLUSIONS These findings suggest that the Detect-TB assay could be applied routinely in reference laboratories across different regions in Brazil.
Asunto(s)
Humanos , Esputo/microbiología , Tuberculosis Pulmonar/diagnóstico , Mycobacterium tuberculosis/aislamiento & purificación , Mycobacterium tuberculosis/genética , Brasil , ADN Bacteriano , Reacciones Falso NegativasRESUMEN
Além de identificar os doentes com tuberculose (TB), é importante monitorar os genótipos de M. tuberculosis circulantes. Mesmo após a implantação do Xpert® MTB/RIF, o diagnóstico é ainda realizado apenas pela baciloscopia, que apresenta baixa sensibilidade, na maioria dos laboratórios. OBJETIVO: Utilizar análises de DNA para o diagnóstico e identificação dos genótipos circulantes em uma população do Rio Grande do Sul, Brasil. METODOLOGIA: Amostras clínicas foram analisadas pelo Detect-TB (Labtest,MG), por PCR em tempo real (Xpert® MTB/RIF) e comparados a baciloscopia. A genotipagem foi realizada por spoligotyping. RESULTADOS: A acurácia do Detect-TB para a identificação da TB foi similarao Xpert® MTB/RIF, sendo que o Detect-TB foi mais custo-efetivo quando utilizado em conjunto com a baciloscopia. Os genótipos LAM5, RDRio e like-Pinni2, relacionados a resistência ao tratamento, estavam sendo transmitidos neste grupo, e a maioria dos resistentes a isoniazida (78,5%)e dos resistentes a rifampicina (92,1%) apresentavam as mutações mais conhecidas. CONCLUSÃO: A aplicação de tecnologias de DNA pode auxiliar no controle de TB, tanto no diagnóstico rápido quanto na identificação de perfis resistentes, viabilizando tratamento adequado aos pacientes.
In addition to detecting patients with tuberculosis (TB), it is important tomonitor circulating M. tuberculosis genotypes. Even after the implantation of Xpert® MTB/RIF, the diagnosis is still based only by bacilloscopy, which have a low sensitivity, in most laboratories. OBJECTIVE: To use DNA analysis for diagnosis and identification of circulating genotypes in a population of Rio Grande do Sul, Brazil. METHODOLOGY: Clinical samples were analyzed by Detect-TB (Labtest,MG), real-time PCR (Xpert® MTB/RIF) and compared to bacilloscopy. Genotyping was performed by spoligotyping. RESULTS: The accuracy of Detect-TB was similar to Xpert® MTB / RIF, butDetect-TB was more cost-effective when used with bacilloscopy. The genotypesLAM5, RDRio and like-Pinni2, related to treatment resistance, were being transmitted among this group, and the majority of the resistant to isoniazid (78.5%) and the resistant to rifampicin (92.1%) presented themost known mutations. CONCLUSION: The application of DNA technologies can help in the controlof TB, both in rapid diagnosis and in the identification of resistant profiles, allowing adequate treatment to the patients.
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Humanos , Tuberculosis , Epidemiología Molecular , Diagnóstico , Resistencia a MedicamentosRESUMEN
Drug-resistant tuberculosis (TB) threatens global TB control and is a major public health concern in several countries. We therefore developed a multiplex assay (LINE-TB/MDR) that is able to identify the most frequent mutations related to rifampicin (RMP) and isoniazid (INH) resistance. The assay is based on multiplex polymerase chain reaction, membrane hybridisation and colorimetric detection targeting of rpoB and katG genes, as well as the inhA promoter, which are all known to carry specific mutations associated with multidrug-resistant TB (MDR-TB). The assay was validated on a reference panel of 108 M. tuberculosis isolates that were characterised by the proportion method and by DNA sequencing of the targets. When comparing the performance of LINE-TB/MDR with DNA sequencing, the sensitivity, specificity and agreement were 100%, 100% and 100%, respectively, for RMP and 77.6%, 90.6% and 88.9%, respectively, for INH. Using drug sensibility testing as a reference standard, the performance of LINE-TB/MDR regarding sensitivity, specificity and agreement was 100%, 100% and 100% (95%), respectively, for RMP and 77%, 100% and 88.7% (82.2-95.1), respectively, for INH. LINE-TB/MDR was compared with GenoType MTBDRplus for 65 isolates, resulting in an agreement of 93.6% (86.7-97.5) for RIF and 87.4% (84.3-96.2) for INH. LINE-TB/MDR warrants further clinical validation and may be an affordable alternative for MDR-TB diagnosis.
Asunto(s)
Proteínas Bacterianas/genética , Catalasa/genética , Farmacorresistencia Bacteriana Múltiple/genética , Mutación/genética , Mycobacterium tuberculosis/genética , Oxidorreductasas/genética , Colorimetría , ADN Bacteriano/genética , Técnicas de Genotipaje , Isoniazida/farmacología , Reacción en Cadena de la Polimerasa Multiplex , Mycobacterium tuberculosis/efectos de los fármacos , Hibridación de Ácido Nucleico , Rifampin/farmacologíaRESUMEN
The occurrence of tuberculosis (TB) in prisons has been described as an alarming public health problem in many countries, especially in developing nations. The objective of this study was to conduct a survey among prisoners with TB respiratory symptoms in order to estimate the incidence of the disease, to analyze the drug susceptibility profile and genotype the isolates of Mycobacterium tuberculosis in the city of Charqueadas, southern of Brazil. The TB incidence was 55/1,900 inhabitants in the prison; this corresponds to an incidence of 3,789/100,000 inhabitants, with a prevalence of 72/1,900 (4,960/100,000 inhabitants). Drug susceptibility test was performed and, among the analyzed isolates, 85% were susceptible to all drugs tested and 15% were resistant to at least one drug, of which 89% were resistant only to isoniazid (INH) or in combination with another drug. The genotype classification of spoligotyping analysis showed that 40% of the isolates belong to LAM family, 22% to T family, 17.5% to Haarlem family, 12.5% to U family and 3% to X family. The shared international spoligotypes most frequently found were 729 (27%), 50 (9.5%), 42 (8%), 53 (8%) and 863 (8%). In conclusion, it was observed that TB in this specific population had been caused, mostly, by strains that have been transmitted in the last few years, as demonstrated by the large level of genotype clustering. In addition, it was found specific large clusters, which were not often found in the general population from the same period and in the same region.
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ADN Bacteriano/análisis , Mycobacterium tuberculosis/genética , Prisioneros/estadística & datos numéricos , Tuberculosis Pulmonar/epidemiología , Adulto , Brasil/epidemiología , Genotipo , Humanos , Masculino , Persona de Mediana Edad , Mycobacterium tuberculosis/efectos de los fármacos , Prevalencia , Tuberculosis Pulmonar/diagnóstico , Adulto JovenRESUMEN
The occurrence of tuberculosis (TB) in prisons has been described as an alarming public health problem in many countries, especially in developing nations. The objective of this study was to conduct a survey among prisoners with TB respiratory symptoms in order to estimate the incidence of the disease, to analyze the drug susceptibility profile and genotype the isolates of Mycobacterium tuberculosis in the city of Charqueadas, southern of Brazil. The TB incidence was 55/1,900 inhabitants in the prison; this corresponds to an incidence of 3,789/100,000 inhabitants, with a prevalence of 72/1,900 (4,960/100,000 inhabitants). Drug susceptibility test was performed and, among the analyzed isolates, 85% were susceptible to all drugs tested and 15% were resistant to at least one drug, of which 89% were resistant only to isoniazid (INH) or in combination with another drug. The genotype classification of spoligotyping analysis showed that 40% of the isolates belong to LAM family, 22% to T family, 17.5% to Haarlem family, 12.5% to U family and 3% to X family. The shared international spoligotypes most frequently found were 729 (27%), 50 (9.5%), 42 (8%), 53 (8%) and 863 (8%). In conclusion, it was observed that TB in this specific population had been caused, mostly, by strains that have been transmitted in the last few years, as demonstrated by the large level of genotype clustering. In addition, it was found specific large clusters, which were not often found in the general population from the same period and in the same region.
Asunto(s)
Adulto , Humanos , Masculino , Persona de Mediana Edad , Adulto Joven , ADN Bacteriano/análisis , Mycobacterium tuberculosis/genética , Prisioneros/estadística & datos numéricos , Tuberculosis Pulmonar/epidemiología , Brasil/epidemiología , Genotipo , Mycobacterium tuberculosis/efectos de los fármacos , Prevalencia , Tuberculosis Pulmonar/diagnósticoRESUMEN
Direct smear examination using Ziehl-Neelsen staining for pulmonary tuberculosis (PTB) diagnosis is inexpensive and easy to use, but has the major limitation of low sensitivity. Rapid molecular methods are becoming more widely available in centralized laboratories, but they depend on timely reporting of results and strict quality assurance obtainable only from costly commercial kits available in high burden nations. This study describes a pre-commercial colorimetric method, Detect-TB, for detecting Mycobacterium tuberculosis DNA in which an oligonucleotide probe is fixed onto wells of microwell plates and hybridized with biotinylated polymerase chain reaction amplification products derived from clinical samples. The probe is capable of hybridising with the IS6110 insertion element and was used to specifically recognise the M. tuberculosis complex. When combined with an improved silica-based DNA extraction method, the sensitivity of the test was 50 colony-forming units of the M. tuberculosis reference strain H37Rv. The results that were in agreement with reference detection methods were observed in 95.2% (453/476) of samples included in the analysis. Sensitivity and specificity for 301 induced sputum samples and 175 spontaneous sputum samples were 85% and 98%, and 94% and 100%, respectively. This colorimetric method showed similar specificity to that described for commercially available kits and may provide an important contribution for PTB diagnosis.
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Mycobacterium tuberculosis/aislamiento & purificación , Hibridación de Ácido Nucleico/métodos , Reacción en Cadena de la Polimerasa/métodos , Esputo/microbiología , Tuberculosis Pulmonar/diagnóstico , Colorimetría , ADN Bacteriano/análisis , Humanos , Mycobacterium tuberculosis/genética , Sondas de Oligonucleótidos/análisis , Juego de Reactivos para Diagnóstico , Sensibilidad y EspecificidadRESUMEN
The present study was carried out to investigate the presence of polymorphism in the N-acetyltransferase gene of 41 clinical isolates of Mycobacterium tuberculosis, that were resistant to isoniazid (INH) with no mutations in the hot spots of the genes previously described to be involved in INH resistance (katG, inhA and ahpC). We observed single nucleotide polymorphisms (SNPs) in ten of these, including the G619A SNP in five isolates and an additional four so far un-described mutations in another five isolates. Among the latter SNPs, two were synonymous (C276T, n=1 and C375G, n=3), while two more non-synonymous SNPs were composed of C373A (LeuâMet) and T503G (MetâArg) were observed in respectively one and two isolates. Molecular modeling and structural analysis based in a constructed full length 3D models of wild type TBNAT (TBNAT_H37Rv) and the isoforms (TBNAT_L125M and TBNAT_M168R) were also performed. The refined models show that, just as observed in human NATs, the carboxyl terminus extends deep within the folded enzyme, into close proximity to the buried catalytic triad. Analysis of tbnat that present non-synonymous mutations indicates that both substitutions are plausible to affect enzyme specificity or acetyl-CoA binding capacity. The results contribute to a better understanding of structure-function relationships of NATs. However, further investigation including INH-sensitive strains as a control group is needed to get better understanding of the possible role of these new mutations on tuberculosis control.
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Antituberculosos/farmacología , Arilamina N-Acetiltransferasa/genética , Farmacorresistencia Bacteriana , Isoniazida/farmacología , Genes Bacterianos , Isoenzimas/genética , Pruebas de Sensibilidad Microbiana , Modelos Moleculares , Mutación , Mycobacterium tuberculosis/genética , Polimorfismo de Nucleótido SimpleRESUMEN
Direct smear examination using Ziehl-Neelsen staining for pulmonary tuberculosis (PTB) diagnosis is inexpensive and easy to use, but has the major limitation of low sensitivity. Rapid molecular methods are becoming more widely available in centralized laboratories, but they depend on timely reporting of results and strict quality assurance obtainable only from costly commercial kits available in high burden nations. This study describes a pre-commercial colorimetric method, Detect-TB, for detecting Mycobacterium tuberculosis DNA in which an oligonucleotide probe is fixed onto wells of microwell plates and hybridized with biotinylated polymerase chain reaction amplification products derived from clinical samples. The probe is capable of hybridising with the IS6110 insertion element and was used to specifically recognise the M. tuberculosis complex. When combined with an improved silica-based DNA extraction method, the sensitivity of the test was 50 colony-forming units of the M. tuberculosis reference strain H37Rv. The results that were in agreement with reference detection methods were observed in 95.2 percent (453/476) of samples included in the analysis. Sensitivity and specificity for 301 induced sputum samples and 175 spontaneous sputum samples were 85 percent and 98 percent, and 94 percent and 100 percent, respectively. This colorimetric method showed similar specificity to that described for commercially available kits and may provide an important contribution for PTB diagnosis.