RESUMO
BACKGROUND: Tuberculosis (TB), especially drug-resistant TB, is a global public health problem. This study aimed to validate a new molecular diagnostic test, the FluoroType® MTBDR. METHOD: Samples underwent routine diagnostic procedures (fluorescence microscopy, culture, species differentiation and phenotypic drug susceptibility testing). Left over samples stored at -20° underwent DNA extraction using the Fluorolyse® kit, followed by FluoroType® MTBDR and Genotype MTBDRplus testing. RESULTS: A total of 350 respiratory and 59 lymph node samples were included in the study; 71 respiratory and 16 lymph node samples were culture positive for M. tuberculosis complex (MTBC). The sensitivity of the FluoroType® MTBDR to detect MTBC DNA was 91.4% (95%CI 82.3-96.8%), 68.4% (95%CI 43.4-87.4%) and 62.5%, (95%CI 35.4-84.8%) for respiratory, smear negative respiratory and lymph node samples respectively. The correlating sensitivities of the GenoType MTBDRplus were 85.9% (95%CI 75.6-93.0%), 52.6% (95%CI 28.9-75.6%) and 56.3% (29.9-80.2). Sensitivity of the FluoroType® MTBDR to detect RMP and INH resistance for respiratory samples was 96.5% (95%CI 82.2-99.9) and 70% (95%CI 45.7-88.1), respectively. The GenoType MTBDRplus revealed sensitivities of 97.1% (95% 85.1-99.9) 70.6% (95%CI 52.5-84.9) for detection of RMP and INH resistance. Indeterminate results were 13/64 (20.3%), 23/64 (35.9%) and 16/64 (25.0%) for rpoB, katG and inhA using the FluoroType® MTBDR. CONCLUSION: The FluoroType® MTBDR has a high sensitivity to detect MTBC DNA. However, the high proportion of indeterminate results across all three genes needs to be addressed.
Assuntos
Técnicas Bacteriológicas , DNA Bacteriano/genética , Linfonodos/microbiologia , Mycobacterium tuberculosis/genética , Escarro/microbiologia , Tuberculose dos Linfonodos/diagnóstico , Tuberculose Pulmonar/diagnóstico , Antituberculosos/farmacologia , Proteínas de Bactérias/genética , Catalase/genética , Análise Mutacional de DNA , DNA Bacteriano/isolamento & purificação , RNA Polimerases Dirigidas por DNA/genética , Farmacorresistência Bacteriana/genética , Genótipo , Humanos , Isoniazida/farmacologia , Mutação , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/isolamento & purificação , Oxirredutases/genética , Fenótipo , Valor Preditivo dos Testes , Reprodutibilidade dos Testes , Rifampina/farmacologia , Espectrometria de Fluorescência , Tuberculose dos Linfonodos/microbiologia , Tuberculose Pulmonar/microbiologiaRESUMO
For Mycobacterium tuberculosis complex (MTBC), the rapid and accurate diagnosis of drug resistance is crucial to ensure early initiation of appropriate therapy. Recently, a new molecular diagnostic test, the FluoroType MTBDR, aimed at detecting rifampin and isoniazid resistance has become available. This study aimed to evaluate the FluoroType MTBDR in comparison to phenotypic drug susceptibility testing (DST) using M. tuberculosis complex isolates. MTBC isolates underwent phenotypic DST and were tested using the FluoroType MTBDR and Genotype MTBDRplus. Sanger sequencing of the key regions of rpoB, katG, inhA, and aphC was performed for isolates with discordant phenotypic and molecular results. Furthermore, isolates with specific wild-type bands missing in the Genotype MTBDRplus, indicating the presence of a mutation, were investigated by Sanger sequencing. Specificity and sensitivity, defined as the proportions of isolates correctly determined as susceptible and resistant by the FluoroType MTBDR compared to phenotypic DST, were calculated. A total of 180 culture isolates were included; phenotypic DST showed 85 isolates susceptible to isoniazid and rifampin, 7 with isoniazid monoresistance, 7 with rifampin monoresistance, and 81 with multidrug resistance. The specificity of the FluoroType MTBDR was 100% (95% confidence interval [CI], 96.0 to 100%) for both rifampin and isoniazid. The sensitivity was 91.7% (95% CI, 83.6 to 96.6%) for isoniazid and 98.9% (95% CI, 93.8 to 100.0%) for rifampin. The FluoroType MTBDR has a high sensitivity and specificity for the detection of rifampin and isoniazid resistance when using culture isolates.
