RESUMEN
Norovirus (NV) is an important cause of acute gastroenteritis in children, but is also frequently detected in asymptomatic children, which complicates the interpretation of NV detection results in both the clinical setting and population prevalence studies. A total of 807 faecal samples from children aged <5 years hospitalized for acute gastroenteritis were collected in Thai Binh, Vietnam, from January 2011 to September 2012. Real-time RT-PCR was used to detect and quantify NV-RNA in clinical samples. A bimodal distribution of cycle threshold (Ct) values was observed in which the lower peak was assumed to represent cases for which NV was the causal agent of diarrhoea, whereas the higher peak was assumed to represent cases involving an alternative pathogen other than NV. Under these assumptions, we applied finite-mixture modelling to estimate a threshold of Ct <21·36 (95% confidence interval 20·29-22·46) to distinguish NV-positive patients for which NV was the likely cause of diarrhoea. We evaluated the validity of the threshold through comparisons with NV antigen ELISA results, and comparisons of Ct values in patients co-infected with rotavirus. We conclude that the use of an appropriate cut-off value in the interpretation of NV real-time RT-PCR results may improve differential diagnosis of enteric infections, and could contribute to improved estimates of the burden of NV disease.
Asunto(s)
Antígenos Virales/análisis , Infecciones por Caliciviridae/diagnóstico , Gastroenteritis/diagnóstico , Norovirus/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa/métodos , Infecciones por Rotavirus/diagnóstico , Rotavirus/genética , Infecciones por Caliciviridae/epidemiología , Infecciones por Caliciviridae/virología , Preescolar , Diagnóstico Diferencial , Ensayo de Inmunoadsorción Enzimática , Heces/virología , Femenino , Gastroenteritis/epidemiología , Gastroenteritis/virología , Humanos , Lactante , Recién Nacido , Masculino , Norovirus/inmunología , Prevalencia , Reacción en Cadena en Tiempo Real de la Polimerasa/métodos , Valores de Referencia , Rotavirus/inmunología , Infecciones por Rotavirus/epidemiología , Infecciones por Rotavirus/virología , Vietnam/epidemiologíaRESUMEN
BACKGROUND & AIMS: Dihydroxy bile acids induce a bicarbonate-rich hypercholeresis when secreted into canalicular bile in unconjugated form; the mechanism is cholehepatic shunting. The aim of this study was to identify a xenobiotic that induces hypercholeresis by a similar mechanism. METHODS: Five organic acids (sulindac, ibuprofen, ketoprofen, diclofenac, and norfloxacin) were infused into rats with biliary fistulas. Biliary recovery, bile flow, and biliary bicarbonate were analyzed. Sulindac transport was further characterized using Tr(-) rats (deficient in mrp2, a canalicular transporter for organic anions), the isolated perfused rat liver, and hepatocyte membrane fractions. RESULTS: In biliary fistula rats, sulindac was recovered in bile in unconjugated form and induced hypercholeresis of canalicular origin. Other compounds underwent glucuronidation and were not hypercholeretic. In the isolated liver, sulindac had delayed biliary recovery and induced prolonged choleresis, consistent with a cholehepatic circulation. Sulindac was secreted normally in Tr(-) rats, indicating that its canalicular transport did not require mrp2. In the perfused liver, sulindac inhibited cholyltaurine uptake, and when coinfused with cholyltaurine, induced acute cholestasis. With both basolateral and canalicular membrane fractions, sulindac inhibited cholyltaurine transport competitively. CONCLUSIONS: Sulindac is secreted into bile in unconjugated form by a canalicular bile acid transporter and is absorbed by cholangiocytes, inducing hypercholeresis. At high flux rates, sulindac competitively inhibits canalicular bile salt transport; such inhibition may contribute to the propensity of sulindac to induce cholestasis in patients.