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BACKGROUND: The Xpert® MTB/RIF rapid molecular test provides a quantitative measure of Mycobacterium tuberculosis (Mtb) DNA in the form of cycle threshold (Ct) values. This information can be translated into mycobacterial load and used as a potential risk measure of bacterial spread for tuberculosis cases, which can impact infection control. However, the role of Ct values in assessing Mtb transmission to close contacts has not yet been demonstrated. METHODS: A prospective study was performed to investigate the association between Xpert® MTB/RIF Ct values and Mtb transmission to close contacts of patients with culture-confirmed pulmonary TB in a multi-center Brazilian cohort. We evaluated clinical and laboratory data, such as age, sex, race, smoking habits, drug use, alcohol use, chest radiograph, Xpert® MTB/RIF results among pulmonary tuberculosis cases, and QuantiFERON(QFT)-Plus results at baseline and after six months for close contacts who had a negative result at baseline. RESULTS: A total of 1,055 close contacts of 382 pulmonary tuberculosis cases were included in the study. The median Ct values from pulmonary tuberculosis cases of QFT-Plus positive (at baseline or six months) close contacts were lower compared with those who were QFT-Plus negative. An adjusted logistic regression demonstrated that reduced Ct values from the index cases were independently associated with QFT-Plus conversion from negative to positive (OR: 1.61, 95% CI: 1.12-2.32) after adjusting for clinical characteristics. CONCLUSION: Close contacts of pulmonary TB index cases exhibiting low Xpert MTB/RIF Ct values displayed higher rates of TB infection, reflecting Mtb transmission.
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Resumen La detección de SARS-CoV-2 y su implicancia en el diagnóstico de COVID-19 han sido muy debatidas en la pandemia. El objetivo de este estudio fue evaluar el costo/beneficio de la detección de SARS-CoV-2 en contactos estrechos asintomáticos (CE) mediante el uso de distintas pruebas de diagnóstico molecular. Se estudiaron 51 CE de personas con diagnóstico de SARS-CoV-2 confirmado por RTqPCR, clasificadas por el umbral de ciclos (Ct) (<20, entre 20 y 30 y >30) en hospitales públicos de la provincia de Buenos Aires. Del total de contactos estudiados el 15,7% resultó confirmado para SARS-CoV-2; no hubo contactos positivos de casos con Ct>30. La cantidad de contactos positivos de casos con Ct<20 fue significativamente mayor que la de casos con Ct>20. Las muestras con Ct<20 se asociaron a una carga viral estimada de entre uno a cuatro órdenes de magnitud de diferencia con los rangos de Ct>20. Un 13,7% de contactos positivos fueron casos con Ct<20. De las muestras positivas confirmadas por PCR, correspondientes a la semana epidemiológica 1 de 2021 (SE1), sólo un 19,35% correspondían a muestras con Ct<20 y un 50,7% con Ct entre 20 y 30. Estos datos muestran un incremento de sólo un 3,7% de casos detectados. El esfuerzo por parte del sistema de salud pública para esta estrategia, con bajo poder predictivo, puede tener un efecto negativo para el cumplimiento del aislamiento de los contactos y podría generar una demora en los resultados de los casos sospechosos, sin aportar significativamente en el control de la pandemia.
Abstract The detection of SARS-CoV-2 and its implication in the diagnosis of COVID-19 have been highly debated in the pandemic. The objective of this study was to evaluate the cost/benefit of detecting SARS-CoV-2 in asymptomatic close contacts (CC) using different molecular diagnostic tests. A total of 51 CC of people with a diagnosis of SARS-CoV-2 confirmed by RTqPCR, classified by the cycle threshold (Ct) (<20, between 20 and 30 and >30), were studied in public hospitals in the Province of Buenos Aires. Of the total contacts studied, 15.7% were confirmed for SARS-CoV-2; there were no positive contacts of cases with Ct>30 positive. The number of positive contacts of cases with Ct<20 was significantly higher than that of cases with Ct>20. Samples with Ct<20 were associated with an estimated viral load of one to four orders of magnitude difference with Ct ranges >20. A total of 13.7% of positive close contacts were from cases with Ct<20. When studying positive samples with confirmed diagnosis by PCR, corresponding to 1 epidemiological week of 2021 (EW1), only 19.35% corresponded to samples with Ct<20 and 50.7% with Ct between 20 and 30. From these data it is shown that with the CC test only 3.7% of the cases were detected. The effort by the public health system for this strategy, with low predictive power, may have a negative effect on the fulfillment of the isolation of contacts and could generate a delay in the results of suspected cases, without contributing significantly to controlling the pandemic.
Resumo A detecção do SARS-CoV-2 e seu envolvimento no diagnóstico da COVID-19 têm sido muito discutidos durante a pandemia. O objetivo desse estudo foi avaliar a relação custo/benefício na detecção de SARSCoV- 2 em casos de contatos próximos assintomático (CP), por meio do uso de diferentes testes de diagnóstico molecular. Foram estudados 51 casos de CP de pessoas com diagnóstico de SARS-CoV-2 confirmado pelo RTqPCR, sendo classificados pelo limiar de ciclos (Ct) (<20, entre 20 e 30 e >30), em hospitais públicos da província de Buenos Aires. Do total de contatos estudados, 15,7% foram confirmados para SARS-CoV-2, não houve contatos positivos de casos com Ct>30. O número de contatos positivos de casos com Ct<20, foi significativamente maior que os casos com Ct>20. As amostras com Ct<20 foram associadas a uma carga viral estimada de uma a quatro ordens de magnitude de diferença com os intervalos de Ct>20. Dos casos positivos, 13,7% foram com Ct<20. Das amostras positivas confirmadas por PCR, correspondentes à semana epidemiológica 1 de 2021 (SE1), apenas 19,35% correspondiam a amostras com Ct>20 e 50,7% com Ct entre 20 e 30. Esses dados mostram incremento de apenas 3,7% de casos detectados. O esforço por parte do sistema de saúde pública para essa estratégia, com baixo poder preditivo, pode ter um efeito negativo no cumprimento do isolamento dos contatos e poderia gerar uma demora nos resultados dos casos suspeitos, sem contribuir significativamente para o controle da pandemia.
Asunto(s)
Virología , SARS-CoV-2 , Aislamiento de Pacientes , Salarios y Beneficios , Sistemas de Salud , Poder Psicológico , Portador Sano , Reacción en Cadena de la Polimerasa , Salud Pública , Carga Viral , Técnicas y Procedimientos Diagnósticos , Costos y Análisis de Costo , Escala de Richter , Técnicas de Diagnóstico Molecular , Diagnóstico , Patología Molecular , Pandemias , Procrastinación , COVID-19 , Hospitales Públicos , PersonasRESUMEN
Atopic dermatitis (AD) is a chronic skin disease that affects up to 20â% of the paediatric population worldwide. Staphylococcus aureus colonizes anterior nares and can be transmitted in the home environment, aggravating AD. This study aimed to detect S. aureus from nares of AD patients and their family contacts, as well as to evaluate the antimicrobial resistance, virulence and clonality of these isolates. Among the 48 family groups investigated, 30 groups were selected, as both the child and his/her respective contact had methicillin-sensitive S. aureus (MSSA) (24 cases; 54 MSSA isolates) or methicillin-resistant S. aureus (MRSA) isolates (6 cases; 13 MRSA isolates). All MRSA isolates carried SCCmec IV. S. aureus carrying PVL genes were detected in 60â% of patients. Pulsed-field gel electrophoresis (PFGE) analysis was performed for 31 isolates from 15 family groups: all 6 with MRSA and 9 with MSSA isolates. Similar genotypic profiles between isolates from patients and their family contacts were noted in 10 (66.6â%) family groups, 5 (83.3â%) of the MRSA family groups and 5 (55.5â%) of the MSSA family groups, indicating that the pathogen was transmitted through family contacts.