RESUMEN
The aim of this study was to investigate the performance of a new and accurate method for the detection of isoniazid (INH) and rifampicin (RIF) resistance among Mycobacterium tuberculosis isolates using a crystal violet decolourisation assay (CVDA). Fifty-five M. tuberculosis isolates obtained from culture stocks stored at -80ºC were tested. After bacterial inoculation, the samples were incubated at 37ºC for seven days and 100 µL of CV (25 mg/L stock solution) was then added to the control and sample tubes. The tubes were incubated for an additional 24-48 h. CV (blue/purple) was decolourised in the presence of bacterial growth; thus, if CV lost its colour in a sample containing a drug, the tested isolate was reported as resistant. The sensitivity, specificity, positive predictive value, negative predictive value and agreement for INH were 92.5%, 96.4%, 96.1%, 93.1% and 94.5%, respectively, and 88.8%, 100%, 100%, 94.8% and 96.3%, respectively, for RIF. The results were obtained within eight-nine days. This study shows that CVDA is an effective method to detect M. tuberculosis resistance to INH and RIF in developing countries. This method is rapid, simple and inexpensive. Nonetheless, further studies are necessary before routine laboratory implementation.
Asunto(s)
Antituberculosos/farmacología , Farmacorresistencia Bacteriana Múltiple/efectos de los fármacos , Violeta de Genciana/normas , Isoniazida/farmacología , Mycobacterium tuberculosis/efectos de los fármacos , Rifampin/farmacología , Antiinfecciosos/farmacología , Proliferación Celular/efectos de los fármacos , Colorimetría/economía , Colorimetría/métodos , Países en Desarrollo , Mycobacterium tuberculosis/aislamiento & purificación , Valor Predictivo de las Pruebas , Proyectos de Investigación , Sensibilidad y EspecificidadRESUMEN
We evaluated Gram stain as a rapid diagnostic method for vulvovaginal candidiasis [VVC]. Vaginal swabs were taken from 100 pregnant women and subjected to Gram stain and culture; 39% were diagnosed as having VVC [29% had symptomatic VVC and 10% had asymptomatic VVC]. Candida albicans was isolated from 94.9% of all cultures while other Candida species were isolated from 5.1% of cases. Multigravidae were significantly more affected than primigravidae. Gram stain is a valuable method in rapid accurate diagnosis of symptomatic VVC and even superior to culture as it demonstrates the invasive forms of the yeast. However, its low sensitivity could restrict its use in routine practice. A combination of culture and Gram stain is the ideal approach for the diagnosis of VVC