A quantitative risk assessment for Escherichia coli O157:H7 in frozen ground beef patties consumed by children under 10 years of age in French households was conducted by a national study group describing an outbreak which occurred in France in 2005. Our exposure assessment model incorporates results from French surveys on consumption frequency of ground beef patties, serving size and consumption preference, microbial destruction experiments and microbial counts on patties sampled from the industrial batch which were responsible for the outbreak. Two different exposure models were proposed, respectively for children under the age of 5 and for children between 5 and 10 years. For each of these two age groups, a single-hit dose-response model was proposed to describe the probability of hemolytic and uremic syndrome (HUS) as a function of the ingested dose. For each group, the single parameter of this model was estimated by Bayesian inference, using the results of the exposure assessment and the epidemiological data collected during the outbreak. Results show that children under 5 years of age are roughly 5 times more susceptible to the pathogen than children over 5 years. Exposure and dose-response models were used in a scenario analysis in order to validate the use of the model and to propose appropriate guidelines in order to prevent new outbreaks. The impact of the cooking preference was evaluated, showing that only a well-done cooking notably reduces the HUS risk, without annulling it. For each age group, a relation between the mean individual HUS risk per serving and the contamination level in a ground beef batch was proposed, as a tool to help French risk managers. 相似文献
Nisin is the only bacteriocin approved as a food preservative because of its antibacterial effectiveness and its negligible toxicity for humans. Typical problems encountered when nisin is directly added to foods are mainly fat adsorption leading to activity loss, heterogeneous distribution in the food matrix, inactivation by proteolytic enzymes, and emergence of resistance in normally sensitive bacteria strains. To overcome these problems, nisin can be immobilized in solid matrices that must act as diffusional barriers and allow controlling its release rate. This strategy allows maintaining a just sufficient nisin concentration at the food surface. The design of such antimicrobial materials must consider both bacterial growth kinetics but also nisin release kinetics. In this review, nisin incorporation in polymer-based materials will be discussed and special emphasis will be on the applications and properties of antimicrobial food packaging containing this bacteriocin. 相似文献
Graft copolymers with a poly(ethylene‐co‐1‐octene) backbone and poly(methyl methacrylate) random polymer branches are successfully synthesized by the grafting‐from technique in the molten state. The in situ radical polymerization of methyl methacrylate from the polyolefin backbone is investigated with two different peroxide initiators at 135 and 150 °C, respectively. The number of PMMA grafts per polyolefin chain is varied from 0.08 to 1.07 with PMMA polymerization degrees of 500 and 18, respectively, depending on the experimental conditions. The effect of a nitroxyl‐based radical scavenger (i.e., DEPN) on competition between the grafting of PMMA from the polyolefin backbone and MMA homopolymerization is also explored.
Derivatives of 5′-aminoadenosine containing methyl carboxylate, methyl phosphonate, gem-bisphosphonate, bis(methylphosphonate), and α-carboxylmethylphosphonate or phosphonoacetate moieties were synthesized from key intermediate 5′-aminonucleoside. These nucleotide analogues were envisaged as 5′-mono- or diphosphate nucleoside mimics. All compounds were evaluated for CD73 inhibition in a cell-based assay (MDA-MB-231) and toward the purified recombinant protein. Most of them failed to reach significant inhibition of AMP hydrolysis by CD73 at 100 μm . Among the new compounds, the most interesting candidates, 5 (5′-deoxy-5′-N-phosphonomethyladenosine) and 7 (5′-deoxy-5′-N-(ethoxyphosphorylacetate)adenosine), inhibited recombinant CD73 by 36 and 46 % and cellular CD73 by 61 and 45 % at 100 μm , respectively. Molecular modeling partially explains this lack of activity, as the initially predicted docking scores had been encouraging, especially for compound 9 . 相似文献
An algorithm is presented, which enables us to use the iterative Richardson method for solving a system of linear algebraic equations with the matrix corresponding to a sign-definite selfadjoint operator, in the absence of information about the lower boundary of the spectrum of the problem. The algorithm is based on the simultaneous operation of two competing processes, the effectiveness of which is constantly analyzed. The elements of linear algebra concerning the spectral estimates, which are necessary to understand the details of the Richardson method with the Chebyshev set of parameters, are presented. The method is explained on the example of a one-dimensional equation of the elliptic type. 相似文献
Sugar‐coated chips : Glycoside clusters are valuable tools for carbohydrate–lectin recognition studies. However, the spatial arrangement of the sugar residues is a key issue in the design of high‐affinity glycoclusters. Here the affinities of linear and antenna‐ and calixarene‐based galactoside clusters towards two lectins derived from Pseudomonas aeruginosa and Ricinus communis were compared by means of glycoarrays.
In this note, we extend the Goyal and Joshi’s model of collaboration networks in oligopoly to multi-market situations. We examine the incentive of firms to form links and the architectures of the resulting equilibrium networks in this setting. We then present some results on efficient networks. 相似文献