Evaluación de la prueba de la nitrato reductasa directa en microplaca para la detección rápida de tuberculosis multirresistente y extensamente resistente a fármacos

Introduction: Reports of Mycobacterium tuberculosis resistant to multiple drugs are increasing globally and laboratories are becoming increasingly aware of the need for drug susceptibility testing. In recent years, due to the long time required by conventional drug susceptibility testing, new approaches have been proposed for faster detection of drug resistance, such as the nitrate reductase assay, considered fast and inexpensive, making it a good diagnostic tool for low resource countries.Objective: The present study proposed a fast direct colorimetric drug susceptibility testing method in a microplate format using solid medium.Materials and methods: The diagnostic accuracy was evaluated by comparing the proportion method with the direct nitrate reductase assay in plates. Frozen sputum samples, known to be positive, were decontaminated and processed by Petroff method. The decontaminated suspension was used to perform direct nitrate reductase assay in 7H11 medium using 1 μg/ml rifampicin (RIF), 0.2 μg/ml isoniazid (INH), 2 μg/ml ofloxacin (OFX), 6 μg/ml kanamycin (KAN), 2 μg/ml amikacin (AMK) and 10 μg/ml capreomycin (CAP). Eighty-four samples were tested and the results for 69% of them were available within 21 days.Results: The sensitivity and specificity compared to the proportion method, was 98.5% and 100% for INH, 98.3% and 96.2% for RIF, 91.7% and 100% for KAN, 78.8% and 97.3% for OFX, 100% and 100% for AMK and CAP, respectively.Conclusion: The results lead to the conclusion that direct nitrate reductase assay, in this new format, is an accurate, quick and inexpensive method to determine the susceptibility profile of M. tuberculosis and may become an alternative for countries with limited resources.Introducción. Los informes sobre Mycobacterium tuberculosis resistente a múltiples fármacos están aumentando a nivel mundial y los laboratorios toman cada vez más conciencia sobre la necesidad de realizar pruebas de sensibilidad a fármacos. Debido al tiempo prolongado que se requiere para hacerlas, se han propuesto nuevos enfoques para la detección rápida de resistencia a los medicamentos, tales como la prueba de la nitrato reductasa.Objetivo. En este estudio se propuso una prueba de sensibilidad a fármacos colorimétrica, rápida y directa, en un formato de microplacas utilizando medio sólido.Materiales y métodos. La precisión del diagnóstico se evaluó mediante la comparación del método de las proporciones con la prueba de la nitrato reductasa directa en placas. Se descontaminaron muestras positivas congeladas de esputo y se procesaron mediante el método de Petroff. La suspensión ya descontaminada se utilizó para hacer la prueba de la nitrato reductasa directa en medio 7H11, utilizando 1 μg/ml de rifampicina, 0,2 μg/ml de isoniacida, 2 μg/ml de ofloxacina, 6 μg/ml de de kanamicina, 2 μg/ ml de amicacina y 10 μg/ml de capreomicina. Se analizaron 84 muestras y los resultados del 69 % de ellas estuvieron disponibles en 21 días.Resultados. La sensibilidad y la especificidad de la prueba comparada con el método de las proporciones fueron de 98,5 y 100 % para la isoniacida, de 98,3 y 96,2 % para la rifampicina, de 91,7 y 100 para la kanamicina, de 78,8 y 97,3 % para la ofloxacina y de 100 y 100 % para la amikacina y la capremicina, respectivamente.Conclusión. Este nuevo formato de la prueba de la nitrato reductasa directa es un método preciso, rápido y económico para determinar el perfil de sensibilidad de M. tuberculosis y puede convertirse en una alternativa para los países con recursos limitados

Fitness of Mycobacterium tuberculosis Strains of the W-Beijing and Non-W-Beijing Genotype

BACKGROUND: Multidrug resistant tuberculosis (MDR-TB) is a major threat for global tuberculosis control. The W-Beijing Mycobacterium tuberculosis genotype has been associated with drug resistance. Elucidation of the mechanisms underlying this epidemiological finding may have an important role in the control of MDR-TB. The aim of this study was to evaluate the fitness of drug-susceptible and MDR M. tuberculosis strains of the W-Beijing genotype compared with that of Non-W-Beijing strains. METHODOLOGY/PRINCIPAL FINDINGS: Fitness of M. tuberculosis strains was determined by evaluating the difference in the growth curves obtained in the MGIT960 automated system and assessing the competitive growth capacity between W-Beijing and non-W-Beijing strains. The W-Beijing MDR strains had a significant longer lag phase duration compared to the other strains but did not present a significant fitness cost. When grown in competition they had an advantage only in medium containing 0.1% Tween 80. CONCLUSIONS/SIGNIFICANCE: It was not possible to confirm a selective advantage of W-Beijing strains to grow, except for differences in their resistance to Tween 80. Further studies are needed to elucidate the putative advantage of W-Beijing strains compared to other genotypes

Respiratory symptoms and active tuberculosis in a prison in Southern Brazil: associated epidemiologic variables

Backgound and Objectives: This study is justified by the high TB prevalence in prisons, which constitutes a public health problem and aims to estimate the prevalence of active tuberculosis (TB) and determine the variables associated with respiratory symptoms in a prison in Brazil. Methods: This is a descriptive study of 262 inmates divided into respiratory symptomatic and asymptomatic groups. Samples were evaluated by microscopy following the cultivation of the sputum from symptomatic individuals. Associated epidemiological variables were also evaluated. Results: Among the 262 inmates included, 178 (68%) were considered symptomatic, and of these, 25 (14%) were diagnosed with active TB. The contribution of culturing in the detection of TB cases was 48%. The prevalence of active TB was 9,542/100.000. Low educational level, use of drugs and alcohol, prison recidivism, and previous TB and HIV-positive status were associated with the presence of respiratory symptoms. Being male, single, black, a prison recidivist, an alcoholic and HIV-seropositive was associated with the development of TB. The rate of TB/HIV co infection was 60%. The outcome was death in 12% of patients. Drug therapy interruption was reported by 96% of patients. Conclusions: The studied population showed a high prevalence of TB and TB/HIV co-infection. In addition, the rates of drug therapy interruption and mortality were alarmingly elevated. KEYWORDS: Epidemiology. Tuberculosis. Coinfections. HIV infection. Prisons

AVALIAÇÃO DA PRESENÇA DE Sporothrix spp. EM SOLO DE ÁREA HIPERENDÊMICA PARA ESPOROTRICOSE NO EXTREMO SUL DO BRASIL

O aumento de casos de esporotricose zoonótica tornou-se um problema de saúde pública em áreas hiperendêmicas para a doença em felinos. O envolvimento dos gatos domésticos nesta transmissão e o contato contínuo destes animais com o solo sugerem que o ambiente possa ser uma importante fonte e/ou reservatório de fungos Sporothrix spp. Assim, este estudo objetivou avaliar a presença de fungos do complexo Sporothrix em amostras de solo provenientes de locais de acesso de felinos infectados no sul do Brasil. Foram coletadas amostras de solo de residências com felinos com esporotricose, de locais próximos a estas residências e também de locais públicos, totalizando 101 amostras. Estas foram processadas pela técnica de plaqueamento direto e incubadas a 25°C por até 15 dias. Dezessete amostras foram paralelamente submetidas a extração de DNA (kitNORGEN BIOTEK CORP(r)) e técnica de PCR espécie-específico e Nested-PCR. Embora em nenhuma amostra avaliada tenha sido detectada a presença de Sporothrix spp., seja por cultivo ou por biologia molecular, este estudo não descarta o papel do ambiente na tríade do processo infeccioso (solo - animal - humano), sendo necessários outros estudos ampliando área de abrangência, volume, tipo e método de coleta das amostras, bem como técnicas de detecção.Palavras-chave: Ambiente; geofílico; S. brasiliensis; S. schenckii

Análise comparativa entre alvos moleculares para detecção do Helicobacter pylori

KEYWORDS: Helicobacter pylori. Polymerase Chain Reaction. Molecular Diagnostic TechniquesDESCRITORES: Helicobacter pylori. Reação em Cadeia da Polimerase. Técnicas de Diagnóstico Molecula