Virulence testing of Listeria monocytogenes

A major problem in understanding foodborne listeriosis from both the basic science and regulatory perspectives revolves around the role played by virulence factors of Listeria monocytogenes and how these interact with host susceptibility to result in the observed incidence of disease. From a mechanistic perspective, this problem has been well investigated, and many virulence components of L. monocytogenes have been discovered. Deletion of these genes results in large reductions in virulence functions in vitro and in vivo. The clonal bacteria and genetically identical hosts necessary to solve the riddles associated with virulence mechanisms are not likely to reflect the natural diversity found among wild populations of L. monocytogenes, including those associated with food. These factors contribute to a major dilemma in risk assessment and risk management of foodborne listeriosis: Although low-level L. monocytogenes contamination of certain foods is relatively common, suggesting widespread exposure, illness is overwhelmingly associated with only a relatively small subpopulation (3 of the 13 L. monocytogenes serotypes) and occurs in only a small proportion of susceptible individuals. Virulence testing based on DNA probes for virulence genes is confounded by the widespread distribution of these genes in food isolates. In terms of the distribution of virulence factors among food isolates of L. monocytogenes, only listeriolysin is well characterized, because beta-hemolysis is often used to confirm the presence of L. monocytogenes in foods. The presence of other virulence genes such as those involved in host cell invasion and cell-to-cell spread (inlA and actA) among food isolates has not been extensively investigated. How the presence of these components translates into functional virulence as measured in vivo and in vitro is also unknown. Animal studies and cell culture systems show a range of virulence among food isolates of L. monocytogenes. However, clinical isolates included in such studies are not consistently more virulent than food isolates with no known human disease association. Where multiple serotypes or ribotypes are compared, it has been difficult to demonstrate a consistent pattern of increased virulence associated with any subtype(s) in animal or in vitro studies. Development of model systems that adequately reflect the complexity of the host-pathogen relationship remains a challenge.     

毛细管电泳技术在疾病预防控制领域的应用、发展与挑战

自1989年出现商品化的仪器以来,毛细管电泳（CE）技术在多个应用领域都取得了长足的进步与发展,重复性和准确性方面也有很大提升。能力验证样品分析的满意结果也显示了CE具备法规要求的准确定量能力。在疾病预防控制领域（简称"疾控"）CE也展现出很多独具特色的应用,成为不可或缺的技术之一。在聚合酶链式反应产物分析、核酸序列测定、DNA变异和分型分析、食源性致病微生物分析及疫苗分析等工作中CE发挥了重要作用。应对突发疫情或公共卫生事件如食物中毒时,除了通过非靶标分析尽快锁定目标物外,还需要对大量样品做出快速而准确的分析,高通量和高灵敏的CE就十分适合解决这一问题。在公共卫生理化检验以确保食品、保健食品、特殊医学用途食品、化妆品和消毒产品等的安全中,CE也发挥了不可或缺的作用。作为一种使用较少危险化学品的环境友好方法,在需要按照标准或规范进行的疾控实验室常规检测中,CE仍受制于标准方法的缺失,未能发挥其应有的作用。但简单、快速、经济、耐用、高效的CE分离一旦与高灵敏通用检测器联用,必将更加从容地应对疾控领域中的各种挑战,发挥更大的作用。本文综述了2010~2019年CE在疾控领域的应用,分析了CE在疾控领域发展的机遇和挑战,对CE在疾控领域的发展前景进行了展望。     

Prediction of African Swine Fever Virus Inhibitors by Molecular Docking-Driven Machine Learning Models

African swine fever virus (ASFV) causes a highly contagious and severe hemorrhagic viral disease with high mortality in domestic pigs of all ages. Although the virus is harmless to humans, the ongoing ASFV epidemic could have severe economic consequences for global food security. Recent studies have found a few antiviral agents that can inhibit ASFV infections. However, currently, there are no vaccines or antiviral drugs. Hence, there is an urgent need to identify new drugs to treat ASFV. Based on the structural information data on the targets of ASFV, we used molecular docking and machine learning models to identify novel antiviral agents. We confirmed that compounds with high affinity present in the region of interest belonged to subsets in the chemical space using principal component analysis and k-means clustering in molecular docking studies of FDA-approved drugs. These methods predicted pentagastrin as a potential antiviral drug against ASFVs. Finally, it was also observed that the compound had an inhibitory effect on AsfvPolX activity. Results from the present study suggest that molecular docking and machine learning models can play an important role in identifying potential antiviral drugs against ASFVs.     

Surveying selenium speciation from soil to cell—forms and transformations

The aim of this review is to present and evaluate the present knowledge of which selenium species are available to the general population in the form of food and common supplements and how these species are metabolized in mammals. The overview of the selenium sources takes a horizontal approach, which encompasses identification of new metabolites in yeast and food of plant and animal origin, whereas the survey of the mammalian metabolism takes a horizontal as well as a vertical approach. The vertical approach encompasses studies on dynamic conversions of selenium compounds within cells, tissues or whole organisms. New and improved sample preparation, separation and detection methods are evaluated from an analytical chemical perspective to cover the progress in horizontal speciation, whereas the analytical methods for the vertical speciation and the interpretations of the results are evaluated from a biological angle as well.     

Bioactive peptides

Peptides with biological activities, released during gastrointestinal digestion or food processing, play an important role in metabolic regulation and modulation, suggesting their potential use as nutraceuticals and functional food ingredients for health promotion and disease risk reduction. Many studies have reported that peptides from various food sources possess bioactivities, including antihypertensive, antioxidant, anticancer, antimicrobial, and opioid activities as well as immunomodulatory and cholesterol-lowering effects. More studies are being performed exploring the sources, bioavailabilities, and possible physiological/functional properties and the mechanisms of action of bioactive peptides. Technological approaches in terms of peptide preparation, purification, and characterization have also been investigated.     

Analytical methods for detection of gluten in food--method developments in support of food labeling legislation

The current essential therapy of celiac disease is a strict adherence to a gluten-free diet. Besides food products that are naturally gluten-free, "very low gluten" and "gluten-free" bakery products have become available. The availability of immunochemical and other analytical methods to determine gluten markers in foods is of utmost importance to ensure the well being of gluten-sensitive individuals. The aim of this review was to evaluate if currently available methodologies are suitable to meet the requirements of food labeling standards for individual gluten source declaration, in order to achieve policy objectives. Codex Alimentarius and European Union (EU) legislation and gluten detection methodologies applicable at present have been summarized and compared. In 2009, the European Commission issued Regulation No. 41/2009 concerning the composition and labeling of foodstuffs suitable for people intolerant to gluten. This review constitutes a basis to investigate the possibility to develop a proteomic-based method for the specific detection of gluten-containing cereals in food products, especially at or around the limits specified in EU legislation.     

Enantioresolution of Amino Acids: A Decade’s Perspective,Prospects and Challenges

Both from academic and industrial points of view enantioseparation of dl-amino acids continues to be a subject of immense importance and enjoys a great analytical significance in various fields, such as in the studies of fossils, origin of life, disease diagnosis, quality of food and beverages, etc. The present paper is a topical collection of recent advances along with a discussion on possible challenges in chiral amino acid analysis and is intended to present the existing state of knowledge on the topic as a particular facet of chromatography (and electrophoretic techniques). It presents a critical overview of the state-of-the-art of the topic, with critically selected examples to point the reader to trends and likely future developments and to give a selection of important references to the current literature.

     

Quality of Fish-Oil-Based Dietary Supplements Available on the Italian Market: A Preliminary Study

The global market of food supplements is growing rapidly with a large turnover. Fish oil supplements represent a significant part of this turnover as they are believed to have important health benefits. Conversely, there are few papers in the literature about the quality control of fish oil capsules. As prior studies illustrate, a perfect agreement with the label is rarely found, and in some isolated cases, large amounts of soybean oil are also detected, indicating a true adulteration rather than a non-compliance with the label. None of the available studies refer to the Italian market, which ranks first in Europe in the consumption of food supplements. In this present communication, a quality control of fish-oil-based supplements from the Italian market was carried out for the first time. With minor deviations, all results showed substantial agreement with the label. However, the most important conclusion from this research is that compliance with the label is not enough to judge a product of good quality. The analysis of the overall fatty acid composition showed that some supplements have a high level of saturated fatty acids, and therefore they did not undergo a proper purification process. This may represent a safety issue since the purification process also allows the removal of toxic contaminants.     

A novel method for the determination of migration of contaminants from food contact materials

A neutron activation method has been developed for the analysis of high density polyethylene, low density polyethylene, polypropylene, polyethylene terephthalate and polystyrene food contact plastics. The method provides determination of over 50 elements at concentrations below 1 mg kg^–1. This technique has now been extended to study migration from food contact materials into standard food simulants (olive oil, acetic acid, ethanol and water). Samples of plastic are irradiated in a thermal neutron flux to produce radionuclides of the elements present in the plastic. Over a period of time the radionuclides of these elements may travel from the plastic into the food simulants, and hence the migration can be determined. Gamma ray spectrometry is performed on the simulants at the end of the test to quantify the migration. Any activity present must be due only to the migration of radionuclides of elements in the plastic and nothing else. This eliminates the need for a blank determination, which is required with existing migration methods. Preliminary studies have shown that detection limits of around 0.002 mg kg^–1 can be achieved for Sb in a retail polyethylene terephthalate (PET) bottle. This can be compared to levels of 0.005     

Preparation,Bioactivities and Applications in Food Industry of Chitosan-Based Maillard Products: A Review

Chitosan, a biopolymer possessing numerous interesting bioactivities and excellent technological properties, has received great attention from scientists in different fields including the food industry, pharmacy, medicine, and environmental fields. A series of recent studies have reported exciting results about improvement of the properties of chitosan using the Maillard reaction. However, there is a lack of a systemic review about the preparation, bioactivities and applications in food industry of chitosan-based Maillard reaction products (CMRPs). The presence of free amino groups in chitosan allows it to acquire some stronger or new functional properties via the Maillard reaction. The present review aims to focus on the current research status of synthesis, optimization and structural identification of CMRPs. The applications of CMRPs in the food industry are also discussed according to their biological and technological properties such as antioxidant, antimicrobial activities and inducing conformational changes of allergens in food. Some promising directions for future research are proposed in this review, aiming to provide theoretical guidance for the further development of chitosan and its derivatives.     

Use of Nuclear Techniques for the Measurement of Trace Elements in Food

Considerable interest in determining levels of trace elements in foods has occurred in the last twenty years. This interest comes from studies attempting to determine the role that elements play in the flavor and in the toxicology of food. Radiochemical methods, like instrumental neutron activation analysis (INAA), are common techniques used to determine dietary trace levels of various elements. A summary of other methods are also referenced in this updated review of past, present, and future uses of radiochemical methods to determine trace elements in food.     

COMPARISON OF THE EFFECTS OF UV-VISIBLE IRRADIATION OF MELANINS and MELANIN-HEMATOPORPHYRIN COMPLEXES FROM HUMAN BLACK and RED HAIR

Clinical evidence indicates that people with light skin and red hair have a higher incidence of UV radiation-induced diseases including cancer. It is not known whether this is because of the lower protection due to the smaller amounts of eumelanin present in the skin of these people or whether the presence of pheomelanin in their skin is responsible for the higher susceptibility to carcinogenesis. Irradiation of melanoproteins from red hair with UV-visible light has been reported to produce superoxide. Comparative studies on the formation of superoxide during the irradiation of the melanins isolated from human black and red hair (BHM and RHM, respectively) are reported in this paper. These showed that no superoxide formation could be detected in the case of the BHM. whereas the formation of superoxide during the irradiation of RHM could be definitely demonstrated. Irradiation of the RHM with NADH resulted in the oxidation of more NADH than the irradiation of NADH with BHM. The observation that RHM is an active photosensitizer indicates that this property of pheomelanin present in light skin may at least partly be responsible for the harmful effect of radiation on people with light skin and/or red hair. Administration of hematoporphyrin followed by visible irradiation is a currently used mode of therapy for cancer. The present studies have shown that hematoporphyrin is bound to both BHM and RHM. The binding of hematoporphyrin to the melanins increased the formation of superoxide by RHM and the oxidation of NADH by both the melanins. The binding of porphyrins to melanins may have an influence upon the photosensitivity in diseases such as porphyrias and may also affect the therapeutic efficacy of hematoporphyrin.     

Nutraceutical Approaches of Autophagy and Neuroinflammation in Alzheimer’s Disease: A Systematic Review

Aging and the emergence of age-associated illnesses are one of the major challenges of our present society. Alzheimer’s disease (AD) is closely associated with aging and is defined by increasing memory loss and severe dementia. Currently, there are no therapy options available that halt AD progression. This work investigates three hallmarks of the disease (autophagy, neuroinflammation, and senescence) and systematically analyzes if there is a beneficial effect from three substances derived from food sources, the so called “nutraceuticals” epigallocatechin gallate, fisetin, and spermidine, on these hallmarks. The results imply a positive outlook for the reviewed substances to qualify as a novel treatment option for AD. A combination of nutraceutical substances and other preventive measures could have significant clinical impact in a multi-layered therapy approach to counter AD.     

Identification of a potent botulinum neurotoxin a protease inhibitor using in situ lead identification chemistry

[reaction: see text] Botulinum neurotoxins (BoNTs), etiological agents of the deadly food poisoning disease botulism, are the most toxic proteins currently known. By using in situ lead identification chemistry, we have uncovered the first class of inhibitors that displays nanomolar potency. From a 15 microM lead compound, structure-activity relationship studies were performed granting the most potent BoNT/A inhibitor reported to date that displays an inhibition constant of 300 nM.     

褪黑素含量测定方法

褪黑素因对人体具有一定的保健功能而作为保健品的主要添加成分被广泛使用。测定褪黑素含量的方法有生化免疫方法、紫外分光光度法、色谱法及色谱-质谱联用法等。主要介绍用气相色谱-质谱联用法、紫外分光光度法和高效液相色谱法测定褪黑素的含量。     

Arsenic concentration and speciation in infant formulas and first foods

Arsenic exposure to humans is pervasive, and, increasingly, studies are revealing adverse health effects at ever lower doses. Drinking water is the main route of exposure for many individuals; however, food can be a significant source of arsenic to an individual, especially if their diet is rice-based. Infants are particularly susceptible to dietary exposure, since many first foods contain rice and they have a low body mass. Here we report on arsenic concentration and speciation in infant formulas and first foods. Speciation is essential for food analysis because of the much greater toxicity of inorganic arsenic species and the possibility that arsenic in food (unlike water) may be present in either inorganic or organic forms. Infant milk formulas were low in total arsenic (2.2-12.6 ng g(-1), n=15). Non-dairy formulas were significantly higher in arsenic than dairy-based formulas. Arsenic in formula was almost exclusively inorganic and predominantly arsenic(V). Arsenic concentration in purees (n=41) and stage 3 foods (n=18) ranged from 0.3-22 ng g(-1). Rice-fortified foods had significantly higher total arsenic concentrations than non rice-based foods. Again arsenic speciation was predominantly inorganic; arsenic(III) was the main species with lower concentrations of DMA and arsenic(V) also present. These data confirm that infants are exposed to arsenic via diet, and suggest that careful attention to diet choices may limit this.     

Behaviour of organic pollutants in paper and board samples intended to be in contact with food

This paper deals with the study of volatile compounds present in a set of three paper and board (P&B) samples of different composition, surface treatment, grammage and thickness. The volatile compounds released by the packaging material (P&B) can be trapped on the food and may then affect the safety and health of consumers. To evaluate if the recycled P&B could be used as food packaging material, adsorption studies have been performed with a selection of chemical substances. The adsorption isotherms are provided. Partition coefficients between paper and air have been calculated for a series of volatile compounds used as model compounds to represent different families of contaminants commonly present in P&B. Values from 4 to 3243 were obtained at different temperatures. The analysis of volatile compounds have been carried out by automatic headspace coupled on-line with GC/MS in SIM mode. The results obtained are shown and discussed.     

Metabolites from Eutypa species that are pathogens on grapes

Structural and synthetic studies of the metabolites isolated from Eutypa lata are reviewed. This fungus is the causative agent of Eutypa dieback disease, also known as eutyposis or dying-arm disease, a perennial canker that affects grapevines and many other woody fruit plants. The review, which encompasses all the literature in this field up to the present and in which 76 references are cited, also includes a detailed study of the biological activity of the metabolites, especially the role of toxins in the development of the plant disease. Some aspects of the synthesis and biosynthesis of these metabolites and related compounds are discussed.     

Applications and Recent Developments in the use of Antibodies for Analysis

ABSTRACT

There are many compounds that require analysis ranging from pesticide levels in corn to disease markers in human patients. There are copious challenges to be met when measuring analytes such as the matrix in which they are to be determined, the amounts present, the cost and the rapidity of the result required. Enzyme immunoassays, immunoaffinity chromatography, immunomagnetic polymerase chain reaction, flow cytometry and immunobiological biosensors have all characteristics that can enhance analytical techniques. Antibody-based methods have found applications in a large number of diverse areas such as food and water analysis, clinical diagnosis and therapeutics The structure and modes of production of antibodies and antibody-based derivatives is described and their applications in analysis critically examined.