食源性致病菌诱导细胞凋亡机理研究进展

细胞凋亡是机体为清理衰老、受损的细胞,维持内环境稳定、确保机体健康而采取的一种有序性“自杀方式”。食源性致病菌进入机体后可通过诱导宿主细胞凋亡以逃离宿主的免疫清除,保证自身生存进而得以在机体内扩散的生存策略。近年来研究表明,食源性致病菌的毒力因子在致病菌诱导宿主细胞凋亡过程中起到非常重要的作用,许多致病菌通过产生相应的毒力因子与凋亡调控因子相结合,引起细胞凋亡的级联反应。本文主要从致病菌毒力因子对凋亡信号通路的影响和调控方面来阐述食源性致病菌诱导细胞凋亡的机理研究进展。     

Emerging foodborne pathogens

The broad spectrum of foodborne infections has changed dramatically over time, as well-established pathogens have been controlled or eliminated, and new ones have emerged. The burden of foodborne disease remains substantial: one in four Americans is estimated to have a significant foodborne illness each year. The majority of these illnesses are not accounted for by known pathogens, so more must remain to be discovered. Among the known foodborne pathogens, those more recently identified predominate, suggesting that as more and more is learned about pathogens, they come under control. In addition to the emergence or recognition of new pathogens, other trends include global pandemics of some foodborne pathogens, the emergence of antimicrobial resistance, the identification of pathogens that are highly opportunistic, affecting only the most high-risk subpopulations, and the increasing identification of large and dispersed outbreaks. New pathogens can emerge because of changing ecology or changing technology that connects a potential pathogen with the food chain. They also can emerge de novo by transfer of mobile virulence factors, often through bacteriophage. Though this is rarely observed, it can be reconstructed. Better understanding of the ecology and dynamics of phage transmission among bacteria will help us to understand the appearance of new pathogens in the future. One may look for emerging foodborne pathogens among the silent zoonoses, and among the severe infections affecting the immunocompromised humans. We should expect the unexpected. In the past, separating human sewage and animal manure from human food and water supplies was critical to improving public health. Now, our health depends increasingly on the safety of the feed and water supplies for the animals themselves. The successes of the 20th century and the new challenges we face mean that public health vigilance, careful investigation of new problems, responsible attention to food safety from farm to table, and partnerships to bring about new foodborne disease control measures will be needed for the foreseeable future.     

副溶血弧菌毒力因子及致病机理的研究进展

副溶血弧菌为一种嗜盐性革兰氏阴性短杆菌,是引发人食源性疾病的主要致病菌之一,主要分布在海洋环境中。副溶血弧菌的毒力因子主要包括黏附因子、侵袭因子、溶血性毒素、尿素酶、脂多糖、外膜蛋白、蛋白酶、Ⅲ型分泌系统和摄铁系统等。本文就副溶血弧菌的主要毒力因子及其致病机理的研究进展进行综述,可为进一步研究该菌的分子致病机理、制定快速精确的检测方法等提供参考。     

Membrane fluidity-related adaptive response mechanisms of foodborne bacterial pathogens under environmental stresses

The maintenance of bacterial membrane fluidity plays an important role in a variety of cell physiological functions such as nutrient transport, protection from external adverse environments, and cell morphology. The fluidity of membranes is modified in response to several environmental cues, enabling bacterial survival in otherwise unfavorable conditions. Many foodborne bacterial pathogens are able to survive a variety of food preservation treatments used to prevent microbial contamination. These pathogens are able to successfully exploit membrane fluidity-related adaptation strategies under unfavorable conditions, resulting in food hygiene failures. Factors involved in food preservation include pH, temperature, osmotic stress, antimicrobial agents, and high pressure. The fluidity of bacterial membrane lipid bilayer is altered mainly via the adjustment of membrane fatty acid composition. Under undesirable conditions, Gram-negative bacteria alter their membrane fluidity primarily by regulating the ratio of unsaturated fatty acids (UFAs) to saturated fatty acids (SFAs) and, to a lesser extent, the levels of cyclopropane fatty acids (CFAs), or by cis/trans isomerization. Gram-positive bacteria typically alter their membrane fluidity with changes in fatty acyl chain length or by forming branched-chain fatty acids (BCFAs), besides changes to the ratio of UFA to SFA. This review encompasses various modulators of membrane fluidity, particularly with respect to foodborne pathogens, which often survive even the hostile environments associated with food processing.     

常见食源性致病菌CRISPR系统结构与功能研究进展

近年发现细菌和古细菌中广泛存在规律成簇间隔的短回文重复序列(clustered regularly interspaced short palindromic repeats,CRISPR)系统,该系统能够有效地防御噬菌体等外源基因元件的入侵,限制基因的水平转移。而在食源性致病菌中CRISPR系统除了免疫防御功能以外,还可能具有调节细菌毒力等的其他功能。并且食源性致病菌的CRISPR系统呈现出的多样性在不同菌株之间存在差异,这种差异为食源性致病菌的遗传进化、分子分型提供了更为可靠的依据。因此,近年来针对食源性致病菌中CRISPR系统结构与功能的研究逐渐成为热点。为了进一步探究CRISPR系统在食源性致病菌中的作用机制与应用前景,本文综述了几种常见的食源性致病菌CRISPR系统的基本结构及相关功能的研究进展。     

乳酸菌拮抗食源性致病菌的研究及应用进展

食品在生产加工、物流运输和贮存消费过程中均可能出现被食源性致病菌污染的风险,造成安全隐患,目前通过热加工、辐照、电解水和等离子体等方法来控制食品中食源性致病菌,但在食品感官、规模化应用和安全生产等方面存在部分缺点.乳酸菌因其丰富的生物活性常作为生物发酵剂和保鲜剂广泛应用于食品中,并且可在食品中拮抗致病菌.本文主要从竞争...     

噬菌体裂解酶结构特征、重组策略及其在控制食源性致病菌中的应用

持续的全球食源性疾病和耐药细菌的广泛流行,对食品安全和人类健康造成了极大的威胁,迫切需要研发新型杀菌、控菌技术。噬菌体裂解酶是大部分裂性噬菌体在裂解期释放一种活性蛋白,能够有效裂解宿主细胞壁,已被证明可应用于食品供应链的各个环节中控制食源性致病菌风险。天然噬菌体裂解酶具有高度的宿主特异性和强烈的裂解活性,能破坏细菌生物被膜,而且具备绿色安全、不易产生耐药等优势。同时,噬菌体裂解酶具有模块化结构特点,运用蛋白质工程技术将其重组,可增强其裂解活性、提高稳定性以及靶向性。本综述系统地描述了噬菌体裂解酶的模块化结构特征及作用位点,讨论了噬菌体裂解酶的重组策略和方法,总结了天然噬菌体裂解酶在控制食源性致病菌方面的应用进展,并对噬菌体裂解酶在食品工业中的应用进行了展望,以期为食源性致病菌及其耐药性的有效控制提供一种行之有效的新策略。     

Risk assessment prediction from genome sequences: promises and dreams

The application of bacterial genomics opens new avenues of research on foodborne pathogens. Foodborne pathogens must be able to colonize their hosts and survive transmission from host to host. Different groups of genes are involved in the processes of survival, colonization, and virulence, and such genes are potential targets for risk assessment and intervention strategies. Filtering from genome sequences the genes relevant to these processes is a major challenge, and although many tools are already available for analyses, this type of data mining is just beginning. For the simplest application, gene comparison, it is important to know how gene function, for instance in virulence, is being defined and tested. In other genomic applications, reserachers look for specific properties or characteristics of (virulence) genes to identify novel gene candidates. Each approach has pitfalls, and gene candidates must be tested in the lab to confirm their function. Models for colonization and virulence are available for most although not all pathogens. Models for survival and stress responses are needed to increase the utilization of genomic approaches to risk assessment. Here, I discuss how genome sequences are likely to help in microbial risk assessment of foodborne pathogens and how dreams may become promises.     

Phages and their lysins: Toolkits in the battle against foodborne pathogens in the postantibiotic era

Worldwide, foods waste caused by putrefactive organisms and diseases caused by foodborne pathogens persist as public health problems even with a plethora of modern antimicrobials. Our over reliance on antimicrobials use in agriculture, medicine, and other fields will lead to a postantibiotic era where bacterial genotypic resistance, phenotypic adaptation, and other bacterial evolutionary strategies cause antimicrobial resistance (AMR). This AMR is evidenced by the emergence of multiple drug-resistant (MDR) bacteria and pan-resistant (PDR) bacteria, which produces cross-contamination in multiple fields and poses a more serious threat to food safety. A “red queen premise” surmises that the coevolution of phages and bacteria results in an evolutionary arms race that compels phages to adapt and survive bacterial antiphage strategies. Phages and their lysins are therefore useful toolkits in the design of novel antimicrobials in food protection and foodborne pathogens control, and the modality of using phages as a targeted vector against foodborne pathogens is gaining momentum based on many encouraging research outcomes. In this review, we discuss the rationale of using phages and their lysins as weapons against spoilage organisms and foodborne pathogens, and outline the targeted conquest or dodge mechanism of phages and the development of novel phage prospects. We also highlight the implementation of phages and their lysins to control foodborne pathogens in a farm–table–hospital domain in the postantibiotic era.     

基于噬菌体的电化学生物传感器在检测食源性病原菌中的研究进展

食源性病原菌是引发食源性疾病暴发的主要原因之一,给人类的生命健康造成极大的威胁,因此其快速准确检测一直备受关注。近年来,电化学生物传感器作为一种快速、灵敏、简便的检测方法已经得到广泛的研究,其研究内容集中于识别元件的开发和固定以及样品的检测应用。噬菌体是一种能特异性侵染细菌的病毒,可将其作为电化学生物传感器中重要的识别元件来开发食源性病原菌的检测方法。与酶、抗体、核酸等识别元件相比,噬菌体更加容易获得,对环境的耐受性强、性质稳定。同时基于噬菌体的阻抗型、安培型等电化学技术因其灵敏度高逐步得到重视和应用。因此,本文着重对噬菌体应用于电化学生物传感器中的固定方法和应用现状进行综述,并对其未来的发展趋势进行展望。     

ADSA Foundation Scholar Award--An integrated science-based approach to dairy food safety: Listeria monocytogenes as a model system

Transmission of food- and milkborne pathogens often involves complex interactions among the pathogen, the environment, and one or multiple host species. A complete understanding of these interactions is critical to allow the development of science-based, effective intervention strategies for foodborne infectious diseases. This article summarizes our studies on the transmission, ecology, pathogenesis and population genetics of Listeria monocytogenes, which we have used as model for a food- and milkborne pathogen that infects multiple hosts and also has considerable ability to survive and multiply in nonhost environments. Application of molecular subtyping tools in conjunction with phenotypic characterization of selected strains has allowed us to define distinct L. monocytogenes subtypes and clonal groups that appear to differ in relevant phenotypic characteristics that may affect their abilities to be transmitted through food systems. For example, a genetic group designated as lineage I has been shown to be not only more common among human listeriosis cases than among animal cases, but lineage I strains also appear to show an increased in vitro ability to spread intracellularly from host cell to host cell. These findings are consistent with the fact that while genetically diverse strains may be classified to one bacterial species, these strains often differ from one another in important genetic and phenotypic characteristics. I thus propose that evolutionary- and molecular subtyping-based definitions of bacterial subtypes and clonal groups will provide critical insight into the microbial ecology of dairy food systems, including not only foodborne pathogens, but also organisms important for dairy fermentation and spoilage.     

金抗肽SIF4对大肠杆菌基于细胞壁靶点的非细胞质膜损伤抑菌机理

为阐明金抗肽SIF₄对食源性大肠杆菌基于细胞壁靶点的非细胞质膜损伤抑菌机理,研究了SIF₄对细胞壁损伤的影响、与细胞壁脂多糖竞争性结合机理及对细胞壁膜组分影响机理,并运用扫描电镜分析了菌体形貌变化。研究发现,SIF₄对菌体细胞壁有破坏作用,在一定浓度范围内,细胞壁受损与SIF₄处理时间和处理剂量呈正相关,且组间差异显著（P<0.05）; SIF₄可与细胞壁脂多糖（LPS）竞争性结合,结合量为256 mg/L或更大时,表现无抑菌活性;傅立叶变换红外光谱（FT-IR）分析发现,SIF₄对细胞壁多糖信息区、蛋白质与脂肪酸混合信息区影响明显,揭示细胞壁是潜在抑菌效应靶点;扫描电镜（SEM）分析发现,SIF₄可破坏菌体细胞壁膜结构并改变菌体形貌。研究认为,SIF₄可基于细胞壁损伤靶点作用于大肠杆菌并实现高效抑菌活性,研究结果可为阐明基于细胞壁靶点的非细胞质膜损伤抑菌机理和食源性大肠杆菌生物防控提供支持。     

Pathogenicity of foodborne Salmonella

Salmonella remains a leading etiological agent in bacterial foodborne diseases. Although human salmonellosis generally presents as a self-limiting episode of enterocolitis, the disease can degenerate into chronic and debilitating conditions. Antibiotic treatment of uncomplicated salmonellosis is contra-indicated because it tends to prolong the carrier state. Clinical management of systemic infections with newer drugs such as third-generation cephalosporins and quinolones is most promising, particularly in light of the increasing resistance of Salmonella to the traditional ampicillin, chloramphenicol and trimethoprim sulfamethoxazole therapeutic agents. Research into the development of effective vaccines from avirulent auxotrophic or from virulence plasmid-cured strains may ultimately facilitate the control of salmonellosis in human populations and in various agricultural sectors. Human salmonellosis reflects the outcome of a confrontation between humoral and cellular immune responses of the host, and virulence determinants of the invasive pathogen. Following an adhesion-dependent attachment of salmonellae to lumenal epithelial cells, the invasive pathogen is internalized within an epithelial cell by a receptor-mediated endocytotic process. Cytotoxin localized in the bacterial cell wall suggestively may facilitate Salmonella entry into the epithelial layer. Cytoplasmic translocation of the infected endosome to the basal epithelial membrane culminates in the release of salmonellae in the lamina propria. During this invasive process, Salmonella secretes a heat-labile enterotoxin that precipitates a net efflux of water and electrolytes into the intestinal lumen. Although non-typhoid salmonellae generally precipitate a localized inflammatory response in deeper tissues via lymphatics and capillaries, and elicit a major immune response. Current research efforts have focused on the molecular characterization and role of virulence plasmids and chromosomal genes in Salmonella pathogenicity.     

Aeromonas species in foods

Aeromonas species have been recognized as potential or emerging foodborne pathogens for more than 20 years. Aeromonads are estuarine bacteria and are ubiquitous in fresh water, fish and shellfish, meats, and fresh vegetables. Actual sourced foodborne outbreaks are few, but epidemiological evidence suggests that the bacterium can cause self-limiting diarrhea, with children being the most susceptible population. Most aeromonads are psychrotrophic and can grow in foods during cold storage. Aeromonads are not resistant to food processing regimes and are readily killed by heat treatment. A host of virulence factors are present, but the exact role of each in human disease has not been fully elucidated.     

A rapid method for determining the antimicrobial activity of novel natural molecules

Preservatives used in the Agro-food industries may be of natural origin or obtained chemically. Because of the increasing interest of consumers in food products that contain only natural ingredients, studies on preservative molecules of natural origin, such as organic acids or peptides, have been reported in the past several years. Such studies, which require numerous assays, may be limited by the large amount of molecules required. Microscale assays provide an opportunity for testing natural components available in low quantity. This study examined a rapid method that used microplates for the evaluation of anti-microbial substances. The method was validated using five foodborne pathogens. It required a low amount of product and was convenient for the determination of correlations between the bacterial growth inhibition and concentration of the antimicrobial substance.     

Resistance responses of microorganisms in food environments.

Food borne microorganisms display a broad spectrum of resistance responses to naturally occurring and intentionally added antimicrobial agents. Resistance may be conferred by innate structural features of the bacterial strain such as an impermeable outer membrane or a mechanism for antibiotic-inactivation. Bacteria previously susceptible to an antimicrobial compound can acquire resistance through mutation or through genetic transfer processes such as transformation, transduction, and conjugation. Resistance can also be conferred by biofilm formation on food processing surfaces as an adaptive response to protect colonies from cleaning and sanitation. Resistant pathogens are a global problem, facilitated by international trade of raw and processed foods. Cross resistance between clinical and nonclinical antimicrobials can exist and is of concern. The development of resistant foodborne pathogens has been attributed to increased antibiotic use in hospitals, outpatient facilities, and veterinary applications. Resistant microorganisms can also develop as a result of physical processes used in food preservation, such as acid treatments and irradiation processes. Strategies to effectively counter resistance development include: changing current practices of antibiotic usage, developing new antibiotics, applying hurdle preservation approaches, preventing bacterial adhesion, and utilizing competitive exclusion. This paper presents an overview of problems arising from the development of microbial resistance, and explores possible solutions for detecting and defeating the adaptive changes of microorganisms.     

泛基因组学在食源性致病菌检测及其耐药监测中的应用

食源性致病菌引起的食源性疾病在全球范围内时有暴发，对致病菌的调查和监测是预防和控制疾病大范围发生的有效手段。然而菌株的遗传变异给监测工作带来了挑战，同时罕见的、未知的菌株信息用传统鉴定方法难以实现。泛基因组学作为新发展的基因组分析方法，提供了更完整的基因组信息，在分离株鉴别、菌株遗传差异研究等方面具有重要贡献。结合数据库与分析软件，泛基因组分析在揭示致病菌的毒力及耐药基因、寻找新的抑菌靶点、监测基因水平转移情况等方面具有很大的应用潜力。本文简要介绍了泛基因组概念和分析方法，综述了其在致病菌快速检测、风险溯源以及风险预警方面的应用，深入阐述了泛基因组分析在耐药性监测和防控领域的发展状况，以期为基于基因组层面的食源性致病菌风险评估提供参考。     

沙门氏菌和单增李斯特菌诱导性耐酸响应机制的研究进展

沙门氏菌和单增李斯特菌被认为是肉制品中最重要的食源性致病菌。它们在弱酸环境下会发生强烈的诱导性耐酸响应,同时诱导产生高毒、耐酸、耐渗透压的高危菌株,是影响消费者健康安全的重大隐患。本文主要从沙门氏菌和单增李斯特菌产生诱导耐酸的发现过程、诱导耐酸响应的危害、产生诱导耐酸的影响因素方面进行概述,进一步从pH值稳态系统、应激蛋白分子的调控及细胞膜组成和流动性调控的角度分析了产生诱导耐酸响应的分子机制。     

陕西省常见食源性致病菌耐药性研究进展

近年来食品安全问题层出不穷,而食源性致病菌则是引起食品安全问题的主要因素之一,严重危害了人类的健康。引发食源性疾病的常见致病菌主要有大肠杆菌、沙门氏菌、金黄色葡萄球菌、单核细胞增生李斯特菌等。研究表明,在过去的几十年里,由于在医疗、养殖业等领域中过度使用抗生素,造成细菌耐药现象日趋严重,这更加重了食源性致病菌的潜在危险。尽管食源性致病菌的耐药性在国家层面有监测网,但是聚焦省级地区仍是以点代面。作者旨在通过综述分析陕西省的食源性致病菌的耐药现状,以期为食源性致病菌耐药性监测提供依据。