Screening of bulk drug samples and anti-tuberculosis products for the presence of therapeutically less active diasteriomeric (R,S) form of ethambutol dihydrochloride.

BACKGROUND: The present study was carried out to screen various ethambutol dihydrochloride (EB2HCI) bulk drug samples and anti-tuberculosis (anti-TB) products for the presence of less active (R,S)-EB2HCl. METHODOLOGY: Samples of pure EB2HCl were received gratis from various companies and the formulations were procured from local market, and also from a Directly Observed Treatment Short-course (DOTS) centre. Some products available in the institute from Global Drug Facility were also included in the study. In total, 5 API samples and 35 formulations containing EB2HCI were investigated. These were subjected to evaluation for the presence of (R,S)-EB2HCl using a previously published differential scanning calorimetric method. The thermograms were recorded between 25 degrees C and 250 degrees C at a rate of 10 degrees C/min. RESULTS: 1 API sample and 12 formulations were found to contain (R,S)-EB2HCI up to an extent of 30-100%. One of the DOTS centres supply was also found to contain approximately 97% of the less active isomer. CONCLUSION: The presence of therapeutically inactive form of the EB2HCl from 30-100% in approximately 30% of the products in the local market is an alarming finding, which means low quality anti-TB products are in circulation. The same may be contributory to the developing resistance of the drugs against the mycobacterium.

Comparative evaluation of the Nitrate Reductase Assay and the Resazurin Microtitre Assay for drug susceptibility testing of Mycobacterium tuberculosis against first line anti-tuberculosis drugs

Tuberculosis remains as a serious infection disease of worldwide distribution, with high morbidity and mortality, mainly in low socio-economic condition countries. The state of emergency of tuberculosis caused by the resistant and multidrug-resistant (MDR) strains, became the main threat to the tuberculosis treatment and control programs. A fast detection method for the resistant strains will allow the implementation of an adequate treatment and contribute for controlling the dissemination of these resistant strains. This study evaluated the performance of the nitrate reductase assay in solid (NRA-LJ) and liquid (NRA-7H9) media, to determine the susceptibility to first line anti-tuberculosis drugs: isoniazid (INH), rifampicin (RMP), ethambutol (EMB) and streptomycin (SMR). Both methods NRA-LJ and NRA-7H9 were evaluated among 18 strains with a known susceptibility profile. The resazurin microtiter assay (REMA) was performed as a reference method. One hundred percent of accordance was observed between NRA-7H9 and REMA for the four tested drugs. When the NRA-LJ method was compared to REMA, the sensitivity and the specificity to INH, RMP, EMB and SMR were 100 percent, 100 percent, 85.7 percent, 76.9 percent and 80 percent, 100 percent, 75 percent and 80 percent, respectively. From the 57 clinical isolates of M. tuberculosis evaluated by NRA-7H9 and REMA, 56 (98.2 percent) were sensitive to all antibiotics tested (INH, RMP, EMB and SMR) by the NRA-7H9 method, while three of these strains were resistant to INH by REMA. One strain showed resistance to INH and RMP for both methods, and MIC of 1.0 µg/ml to INH for both methods, while MIC of 1.0 and 2.0 µg/ml to RMP for REMA and NRA-7H9, respectively. The three assays showed a high level of agreement for rapid detection of rifampicin and isoniazid resistance. Regarding rapidness, the detection of color change in the NRA method is within instants as compared to the overnight incubation required...

A tuberculose permanece como uma séria doença infecciosa, com distribuição mundial, alta morbidade e mortalidade, ocorrendo principalmente em paises com baixa condição econômica. O estado de emergência da tuberculose causada por cepas resistentes e multirresistentes tornou-se uma importante ameaça para o tratamento e programas de controle da tuberculose. Uma rápida detecção de cepas resistentes permitirá a implantação de um tratamento adequado e contribuirá para controlar a disseminação destas cepas. Este estudo avaliou a performace do ensaio nitrato redutase em meio sólido (NRA-LJ) e meio líquido (NRA-7H9), para determinar a sensibilidade frente aos fármacos antituberculosos de primeira linha: isoniazida (INH), rifampicina (RMP), etambutol (EMB) and estreptomicina (SMR). Ambos os métodos, NRA-LJ e NRA-7H9, foram avaliados com 18 cepas com conhecido perfil de sensibilidade. O ensaio de microplaca com resazurina (REMA) foi utilizado como método de referência. A concordância observada entre NRA-7H9 and REMA foi de 100 por cento para os quatro fármacos testados. Quando o método NRA-LJ foi comparado com o REMA, a sensibilidade e especificidade para INH RMP e SMR foram de 100 por cento, 100 por cento, 85,7 por cento, 76,9 por cento e 80 por cento, 100 por cento, 75 por cento and 80 por cento, respectivamente. Dos 57 isolados clinicos de M. tuberculosis avaliados por NRA-7H9 e REMA, 56 (98.2 por cento) foram sensíveis a todos antibióticos testados (INH, RMP, EMB e SMR) pelo método NRA-7H9, enquanto três destas cepas foram resistentes para INH pelo REMA. Uma cepa mostrou resistência para INH e RMP por ambos os métodos, e CMI de 1,0 µg/ml para INH para ambos os métodos, enquanto CMI de 1,0 e 2,0 µg/ml para RMP pelo REMA e NRA-7H9, respectivamente. Os três ensaios mostraram um alto nível ded concordância para uma rápida detecção de resistência a rifampicina e isoniazida. Com relação à rapidez na obtenção dos resultados, a detecção na mudança de...