Comprehensive Analysis of a Norovirus-Associated Gastroenteritis Outbreak,from the Environment to the Consumer

Noroviruses have been recognized to be the predominant agents of nonbacterial gastroenteritis outbreaks in humans, and their transmission via contaminated shellfish consumption has been demonstrated. Norovirus laboratory experiments, volunteer challenge studies, and community gastroenteritis outbreak investigations have identified human genetic susceptibility factors related to histo-blood group antigen expression. Following a banquet in Brittany, France, in February 2008, gastroenteritis cases were linked to oyster consumption. This study identified an association of the norovirus illnesses with histo-blood group expression, and oyster contamination with norovirus was confirmed by qualitative and quantitative analyses. The secretor phenotype was associated with illness, especially for the non-A subgroup. The study showed that, in addition to accidental climatic events that may lead to oyster contamination, illegal shellfish collection and trading are also risk factors associated with outbreaks.Since they were first identified as the cause of a gastroenteritis outbreak in an elementary school in Norwalk, OH, in 1968, noroviruses (NoVs) have come to be recognized as important agents of nonbacterial gastroenteritis in humans (3). NoVs are small nonenveloped viruses containing a single-stranded, positive-sense RNA genome and constitute one of the six genera in the family Caliciviridae. On the basis of genomic sequence and phylogenetic analyses, the NoV genus contains more than 30 genetic types distributed into five genogroups, and they cause infection principally in humans but also in some animals (46). Since the end of the last century, genogroup II (GII) strains have predominated among humans, but numerous strains presenting genomic diversity cocirculate in the population. Many NoV strains bind to histo-blood group antigens (HBGAs) (40). HBGAs are complex glycans present on many cell types, including red blood cells and vascular endothelial cells, as well as on the epithelia of the gastrointestinal, urogenital, and respiratory tracts. HBGAs are synthesized from a series of precursor structures by the stepwise addition of monosaccharide units via a set of glycosyltransferases. In humans, the pleiotropic interaction of alleles at three loci, FUT3, FUT2, and ABO, determines the Lewis, secretor, and ABO phenotypes, respectively (28). The evidence that has accumulated from volunteers studies and from the analysis of outbreaks indicates that binding to these carbohydrates is required for infection (5, 6, 15, 17, 18, 25, 39). Moreover, various human NoV strains that bind to HBGAs present distinct specificities for HBGAs (13, 14, 38). As a result, most strains infect only a subset of the population, on the basis of HBGA expression (9, 24, 40). In addition, some strains of either GI or GII were shown to specifically attach to oyster tissues through the recognition of histo-blood group antigens (21, 30, 43, 44), suggesting that oysters may act as selective filters, specifically concentrating strains that can recognize carbohydrate epitopes shared with humans.NoV infection is characterized by the sudden onset of vomiting or diarrhea, or both symptoms (3). Similar to other viruses causing gastroenteritis, NoVs multiply in the intestines and are excreted in large quantities in human feces. Human waste is processed in sewage treatment plants, but the treatment procedures do not completely remove enteric viruses from the water effluents leaving the plant (8, 16). Strains that cause severe symptomatic infections as well as those that cause subclinical infections are excreted into sewage, which may then be discharged into coastal environments (11). As these viruses are very resistant to inactivation, the sanitary consequences can include contamination of drinking water, vegetables, and bivalve molluscan shellfish (19). Mollusks such as oysters filter large volumes of water as part of their feeding activities and are able to accumulate and concentrate different types of pathogens. Regulations based on measurement of the levels of bacterial enteric pathogens in shellfish tissues (European regulation 54/2004/EC) or in water in which shellfish are grown (United States National Sanitation Program) have been instituted to protect consumers. However, despite these control measures, outbreaks linked to shellfish consumption still occur after either accidental contamination or incomplete depuration (22, 34, 45). Illegal shellfish collection and trading represent an additional source of food contamination that has received little attention so far. We report here on a norovirus outbreak that was due to a breach of such a regulation. In addition, quantitative data on oyster contamination and the number of oysters consumed in relation to the genetic susceptibility of exposed consumers are reported.     

Clinical predictors of and mortality in acute respiratory distress syndrome: potential role of red cell transfusion

OBJECTIVE: Clinical predictors for acute respiratory distress syndrome (ARDS) have been studied in few prospective studies. Although transfusions are common in the intensive care unit, the role of submassive transfusion in non-trauma-related ARDS has not been studied. We describe here the clinical predictors of ARDS risk and mortality including the role of red cell transfusion. DESIGN: Observational prospective cohort. SETTING: Intensive care unit of Massachusetts General Hospital. PATIENTS: We studied 688 patients with sepsis, trauma, aspiration, and hypertransfusion. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Two hundred twenty-one (32%) subjects developed ARDS with a 60-day mortality rate of 46%. Significant predictors for ARDS on multivariate analyses included trauma (adjusted odds ratio [ORadj] 0.22, 95% confidence interval [CI] 0.09-0.53), diabetes (ORadj 0.58, 95% CI 0.36-0.92), direct pulmonary injury (ORadj 3.78, 95% CI 2.45-5.81), hematologic failure (ORadj 1.84, 95% CI 1.05-3.21), transfer from another hospital (ORadj 2.08, 95% CI 1.33-3.25), respiratory rate >33 breaths/min (ORadj 2.39, 95% CI 1.51-3.78), hematocrit >37.5% (ORadj 1.77, 95% CI 1.14-2.77), arterial pH <7.33 (ORadj 2.00, 95% CI 1.31-3.05), and albumin 相似文献   

Rotavirus-specific B cells induced by recent infection in adults and children predominantly express the intestinal homing receptor alpha4beta7

In vivo replication of rotaviruses is generally limited to enterocytes. Because of this restriction, most blood circulating rotavirus-specific B cells are hypothesized to originate in Peyer's patches and should express the intestinal homing receptor alpha4beta7. To test this hypothesis in humans, we used a flow cytometry assay that identifies antigen-activated (IgD-) B cells (CD19+) that express surface rotavirus-specific immunoglobulin. With this assay we could detect rotavirus-specific B cells in both children and adults with an acute rotavirus (RV) infection. Staining with an anti-alpha4beta7 monoclonal antibody, we could determine that B cells that express rotavirus-specific surface immunoglobulin predominantly express alpha4beta7. The response of rotavirus-specific antibody-secreting cells in the peripheral blood of children and adults with acute rotavirus infection was also studied by ELISPOT. The antibody-secreting cells of children were mainly of the IgM isotype, while the antibody-secreting cells of adults were predominantly of the IgA and IgG isotype. alpha4beta7+ and alpha4beta7- subsets of peripheral blood mononuclear cells were purified using paramagnetic beads and then tested in the ELISPOT assay. Rotavirus-specific antibody-secreting cells were predominantly present in the alpha4beta7+ subpopulation. The flow cytometry assay we have described will permit future studies to characterize the phenotype of virus-specific B cells and could be useful in the study of the immunogenicity and protective efficacy of RV vaccines and the identification of markers of protective immunity.     

Comparison of cell culture with two direct Chlamydia tests using immunofluorescence or enzyme-linked immunosorbent assay

Two direct tests for diagnosis of infection due to Chlamydia trachomatis were evaluated on 417 specimens collected from a population with a low disease prevalence of 8.1 %. The intensity of positive results was graded according to the number of inclusions or elementary bodies and the optical density of the reaction. Thirty-four specimens were positive in cell culture, 39 positive with MicroTrak and 43 positive with Chlamydiazyme assay. The sensitivity of the two direct tests was 91.2 % (31 of 34); the specificity was 97.9 % (381 of 389) for MicroTrak and 96.9 % (377 of 389) for Chlamydiazyme assay. The positive predictive values were 79.5 % (31 of 39) for MicroTrak and 72.1 % (31 of 43) for Chlamydiazyme assay. None of the specimens negative by the culture method were positive by the two direct methods. Discrepancies were restricted to the slightly positive specimens. The direct tests seem to be an alternative for diagnosing Chlamydia trachomatis infections, but slightly positive results require cell culture confirmation.     

Comparison of two new tests for rapid diagnosis of respiratory syncytial virus infections by enzyme-linked immunosorbent assay and immunofluorescence techniques.

The sensitivity and the specificity of two new commercial reagent tests, an indirect fluorescent antibody test (FAT) with a mouse monoclonal antibody (MAb) against respiratory syncytial virus (RSV) and an enzyme-linked immunosorbent assay (ELISA) RSV antigen detection kit, were determined by a comparison of results from these tests with those of tissue culture isolation and an indirect FAT with bovine polyclonal antibody (BPA). Of 251 nasal aspirates from infants with suspected RSV infection, positive results were found for 99 (39%) by the FAT-MAb, 93 (37%) by the FAT-BPA, and 87 (35%) by the ELISA; 69 of 240 (29%) were positive by cultures. The FAT-MAb was a more sensitive technique than cultures, with 87% sensitivity for the FAT-MAb and 84% for the ELISA. It was also more sensitive than the FAT-BPA, with 97% sensitivity for the FAT-MAb and 85% for the ELISA. This could be caused only by the distinctive volume of suspended specimens used in these tests. Of 171 negative culture specimens, positive (but not false-positive) results were found for 18% by the FAT-MAb and for 12% by the ELISA. Inversely, 13% of 69 culture positive specimens were FAT-MAb negative and 16% were ELISA negative, emphasizing the importance of tissue cultures for the maximum recovery of RSV, as well as for detection of other respiratory viruses. The FAT-MAb and ELISA were easy to perform and interpret, thus facilitating wider use.