RESUMO
In this study we evaluated the crystal violet decolorization assay (CVDA) for detection of minimum inhibitory concentration (MIC) of antituberculosis drugs. 53 isolates were tested in this study and 13 of them were multidrug resistant (MDR) isolates. The antibiotics concentrations were 2-0.06 mg/L for isoniazid (INH) and rifampicin (RIF) and were 16-0.25 mg/L for streptomycin (STM) and ethambutol (EMB). Crystal violet (CV-25 mg/L) was added into the microwells on the seventh day of incubation and incubation was continued until decolorization. Decolorization of CV was the predictor of bacterial growth. Overall agreements for four drugs were detected as 98.1%, and the average time was detected as 9.5 ± 0.89 day after inoculation. One isolate for INH and two isolates for STM were determined resistant in the reference method, but susceptible by the CVDA. One isolate was susceptible to EMB by the reference method, but resistant by the CVDA. All results were concordant for RIF. This study shows that CVDA is a rapid, reliable and suitable for determination of MIC values of Mycobacterium tuberculosis. And it can be used easily especially in countries with limited-sources.
Assuntos
Humanos , Antituberculosos/farmacologia , Mycobacterium tuberculosis/efeitos dos fármacos , Antituberculosos/administração & dosagem , Bioensaio , Farmacorresistência Bacteriana Múltipla/efeitos dos fármacos , Etambutol/administração & dosagem , Etambutol/farmacologia , Violeta Genciana/química , Indicadores e Reagentes/química , Isoniazida/administração & dosagem , Isoniazida/farmacologia , Testes de Sensibilidade Microbiana/métodos , Mycobacterium tuberculosis/crescimento & desenvolvimento , Rifampina/administração & dosagem , Rifampina/farmacologia , Estreptomicina/administração & dosagem , Estreptomicina/farmacologia , Tuberculose Resistente a Múltiplos Medicamentos/microbiologiaRESUMO
The purpose of this study is to evaluate four rapid colourimetric methods, including the resazurin microtitre assay (REMA), malachite green decolourisation assay (MGDA), microplate nitrate reductase assay (MNRA) and crystal violet decolourisation assay (CVDA), for the rapid detection of multidrug-resistant (MDR) tuberculosis. Fifty
Assuntos
Humanos , Antituberculosos/farmacologia , Farmacorresistência Bacteriana Múltipla/efeitos dos fármacos , Testes de Sensibilidade Microbiana/métodos , Mycobacterium tuberculosis/efeitos dos fármacos , Corantes , Indicadores e Reagentes , Sensibilidade e EspecificidadeRESUMO
Early detection of drug resistance in Mycobacterium tuberculosis isolates allows for earlier and more effective treatment of patients. The aim of this study was to investigate the performance of the malachite green decolourisation assay (MGDA) in detecting isoniazid (INH) and rifampicin (RIF) resistance in M. tuberculosis clinical isolates. Fifty M. tuberculosis isolates, including 19 multidrug-resistant, eight INH-resistant and 23 INH and RIF-susceptible samples, were tested. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and agreement of the assay for INH were 92.5%, 91.3%, 92.5%, 91.3% and 92%, respectively. Similarly, the sensitivity, specificity, PPV, NPV and agreement of the assay for RIF were 94.7%, 100%, 100%, 96.8% and 98%, respectively. There was a major discrepancy in the tests of two isolates, as they were sensitive to INH by the MGDA test, but resistant by the reference method. There was a minor discrepancy in the tests of two additional isolates, as they were sensitive to INH by the reference method, but resistant by the MGDA test. The drug susceptibility test results were obtained within eight-nine days. In conclusion, the MGDA test is a reliable and accurate method for the rapid detection of INH and RIF resistance compared with the reference method and the MGDA test additionally requires less time to obtain results.
Assuntos
Antituberculosos/farmacologia , Farmacorresistência Bacteriana Múltipla/efeitos dos fármacos , Isoniazida/farmacologia , Mycobacterium tuberculosis/efeitos dos fármacos , Rifampina/farmacologia , Corantes de Rosanilina/farmacologia , Testes de Sensibilidade Microbiana/métodos , Valor Preditivo dos Testes , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
The microplate nitrate reductase assay (MNRA) and the rezasurin microtitre assay (REMA) were used for the susceptibility testing of 73 clinical isolates and the results were compared with those that were obtained using the Bactec 460 TB and Bactec MGIT 960 systems. The REMA and the MNRA were performed in 96-well plates. For the REMA, the concentrations of isoniazid (INH) and rifampicin (RIF) ranged from 1.0-0.01 µg/mL and 2.0-0.03 µg/mL, respectively. For the MNRA, the INH concentration was between 1.0-0.03 µg/mL and the RIF concentration was between 2.0-0.06 µg/mL. For the MNRA, the sensitivity, specificity, positive predictive value, negative predictive value and INH/RIF agreement were 100/95.6, 97.6/100, 96.8/100, 100/98 and 98.6/98.6, respectively, and for the REMA, they were 100/91.3, 90.4/100, 88.5/100, 100/96.1 and 94.5/97.2, respectively. Our data suggest that these two rapid, low-cost methods may be inexpensive, alternative assays for the rapid detection of multidrug resistant tuberculosis in low-income countries.
Assuntos
Humanos , Antituberculosos/farmacologia , Farmacorresistência Bacteriana Múltipla/efeitos dos fármacos , Isoniazida/farmacologia , Testes de Sensibilidade Microbiana/métodos , Mycobacterium tuberculosis/efeitos dos fármacos , Rifampina/farmacologia , Mycobacterium tuberculosis/isolamento & purificação , Nitrato Redutase/metabolismo , Oxazinas/metabolismo , Valor Preditivo dos Testes , Kit de Reagentes para Diagnóstico , Sensibilidade e Especificidade , Tuberculose Resistente a Múltiplos Medicamentos/microbiologia , Xantenos/metabolismoRESUMO
The susceptibility of 49 Mycobacterium tuberculosis clinical isolates to isoniazid (INH) and rifampisin (RIF) (28 multi-drug resistant-tuberculosis samples) was determined by a nitrate reductase assay (NRA) on blood agar. Agreement between the NRA and other testing methods was found to be 93.8 percent for both INH and RIF. The sensitivity, specificity, positive predictive value and negative predictive value for INH were 92.8 percent, 94.2 percent, 86.6 percent and 97 percent, respectively. The sensitivity, specificity, positive predictive value and negative predictive value for RIF were 90.4 percent, 96.4 percent, 95 percent and 93.1 percent. In conclusion, we show here that blood agar can be used effectively for the NRA test.