Ecology of Escherichia coli O157:H7 in commercial dairies in southern Alberta

Shedding of Escherichia coli O157:H7 was monitored monthly over a 1-yr period by collecting pooled fecal pats (FECAL) and manila ropes orally accessed for 4 h (ROPE) from multiple pens of cattle in 5 commercial dairies in southern Alberta, Canada. Using immunomagnetic separation, E. coli O157:H7 was isolated from cows on 4 of the dairies and from 13.5% of FECAL and 1.1% of ROPE samples. Pulsed-field gel electrophoresis of XbaI- and SpeI-digested bacterial DNA of the 65 isolates produced 23 unique restriction endonuclease digestion patterns, although 92% of the isolates belonged to 3 restriction endonuclease digestion pattern clusters sharing a minimum 90% homology. Collection of positive isolates was 15 times more likely from June through September. Across dairies, peak somatic cell count occurred in July, August, September, and November. The likelihood of positive isolates was 2.6 times higher in calves and heifers compared with mature cows. This study indicates that ROPE would be of little value for the detection of E. coli O157:H7 in dairy herds unless oral contact with ROPE could be increased in mature animals. Additionally, mitigation strategies for E. coli O157:H7 should be targeted to the months of July, August, and September and toward immature animals for maximum impact. All farms displayed unique combinations of seasonality of shedding and diversity of E. coli O157:H7 subtypes. The fact that seasonal prevalence of E. coli O157:H7 largely coincided with peak somatic cell count within climatically controlled dairy barns suggests that similar environmental factors may be enhancing fecal shedding E. coli O157:H7 and the incidence of mastitis.     

Phytotoxin Production and Phytoalexin Elicitation by the Phytopathogenic Fungus Sclerotinia sclerotiorum

The fungus Sclerotinia sclerotiorum (Lib.) de Bary causes rot disease in a vast range of plant families, including Cruciferae (Brassicaceae). We investigated the production of phytotoxins by S. sclerotiorum by using a bioassay-guided isolation, as well as the phytoalexins produced by the resistant wild crucifer Erucastrum gallicum under elicitation by S. sclerotiorum and other agents. We established for the first time that S. sclerotiorum produces a somewhat selective phytotoxin, sclerin, which is phytotoxic to three cruciferous species (Brassica napus, B. juncea, and Sinapis alba) susceptible to Sclerotinia stem rot disease, causing severe necrosis and chlorosis, but not to a resistant species (Erucastrum gallicum). In addition, we have shown that oleic acid, the major fatty acid isolated from sclerotia of S. sclerotiorum is responsible for the toxic activity of extracts of sclerotia to brine shrimp larvae (Artemia salina). Phytoalexin elicitation in leaves of E. gallicum led to the isolation of three known phytoalexins: indole-3-acetonitrile, arvelexin, and 1-methoxyspirobrassinin. Considering that resistance of E. gallicum to S. sclerotiorum is potentially transferable to B. rapa, a susceptible canola species, and that arvelexin, and 1-methoxyspirobrassinin are not produced by B. rapa, these phytoalexins may become useful markers for resistance against S. sclerotiorum.     

Dietary pectic substances enhance gut health by its polycomponent: A review

Pectic substances, one of the cell wall polysaccharides, exist widespread in vegetables and fruits. A surge of recent research has revealed that pectic substances can inhibit gut inflammation and relieve inflammatory bowel disease symptoms. However, physiological functions of pectins are strongly structure dependent. Pectic substances are essentially heteropolysaccharides composed of homogalacturonan and rhamnogalacturonan backbones substituted by various neutral sugar sidechains. Subtle changes in the architecture of pectic substances may remarkably influence the nutritional function of gut microbiota and the host homeostasis of immune system. In this context, developing a structure–function understanding of how pectic substances have an impact on an inflammatory bowel is of primary importance for diet therapy and new drugs. Therefore, the present review has summarized the polycomponent nature of pectic substances, the activities of different pectic polymers, the effects of molecular characteristics and the underlying mechanisms of pectic substances. The immunomodulated property of pectic substances depends on not only the chemical composition but also the physical structure characteristics, such as molecular weight (M_w) and chain conformation. The potential mechanisms by which pectic substances exert their protective effects are mainly reversing the disordered gut microbiota, regulating immune cells, enhancing barrier function, and inhibiting pathogen adhesion. The manipulation of pectic substances on gut health is sophisticated, and the link between structural specificity of pectins and selective regulation needs further exploration.     

食源性人兽共患病病原检测方法研究进展

食源性人兽共患病(food-borne zoonoses)是指摄入被人与脊椎动物共同病原微生物污染的食物,在人与脊椎动物之间相互传播的疾病。随着饮食习惯以及畜牧业的发展,食源性人兽共患病对食品安全、人类公共卫生安全以及畜牧业的持续发展发起了更加严峻的挑战。近几年全球范围内食源性人兽共患病的传播,正是由人类的不良饮食习惯、对人与自然和谐共处意识的缺乏、对公共卫生风险防控能力的不足所导致的。因此,了解目前对食源性人兽共患病的防治措施及防控检测手段,进一步开发拓展对食源性人兽共患病病原安全有效、快速、经济的检测方法是十分必要的。本文主要综述了近年以细菌、病毒、寄生虫为代表的食源性人兽共患病病原的常用检测手段,为食品质量安全控制提供了参考,同时也为新技术的开发提供了研究基础。     

Muscodor albus Volatiles Control Toxigenic Fungi under Controlled Atmosphere (CA) Storage Conditions

Muscodor albus, a biofumigant fungus, has the potential to control post-harvest pathogens in storage. It has been shown to produce over 20 volatile compounds with fungicidal, bactericidal and insecticidal properties. However, M. albus is a warm climate endophyte, and its biofumigant activity is significantly inhibited at temperatures below 5 °C. Conidia of seven mycotoxin producing fungi, Aspergillus carbonarius, A. flavus, A. niger, A. ochraceus, Penicillium verrucosum, Fusarium culmorum and F. graminearum, were killed or prevented from germinating by exposure to volatiles from 2 g M. albus-colonized rye grain per L of headspace in sealed glass jars for 24 h at 20 °C. Two major volatiles of M. albus, isobutyric acid (IBA) and 2-methyl-1-butanol (2MB) at 50 μL/L and 100 μL/L, respectively, gave differential control of the seven fungi when applied individually at 20 °C. When the fungi were exposed to both IBA and 2MB together, an average of 94% of the conidia were killed or suppressed. In a factorial experiment with controlled atmosphere storage (CA) at 3 °C and 72 h exposure to four concentrations of IBA and 2MB combinations, 50 μL/L IBA plus 100 μL/L 2MB killed or suppressed germination of the conidia of all seven fungi. Controlled atmosphere had no significant effect on conidial viability or volatile efficacy. Major volatiles of M. albus may have significant potential to control plant pathogens in either ambient air or CA storage at temperatures below 5 °C. However, combinations of volatiles may be required to provide a broader spectrum of control than individual volatiles.     

SLUDGE TREATMENT AND DRYING REED BED SYSTEMS IN DENMARK

Sludge Reed beds have been used for dewatering (draining and evapotranspiration) and mineralisation of sludge in Denmark since 1988 when the first sludge processing system was introduced. Sludge from wastewater treatment plants (2,500-125,000 pe) is treated in sludge reed bed systems with 1–18 basins with loading rates of 25–2,200 tonnes dry solids/year for ten years. In 2002, approximately 95 systems were in operation. Dimensioning and design of reed bed systems depends on the sludge production rate, sludge type, quality and regional climate.
The maximum sludge loading rate is approximately 50–60 kg DS/m²/year. Loading cycles are related to the sludge type and the age of the sludge reed systems. The sludge residue will, after approximately ten years of operation, reach an approximate height of 1.2–1.5 metres with dry solids content of 30–40%. Experience has shown that the quality of the final product with respect to heavy metals, hazardous organic compounds and pathogen removal after ten years of treatment make it possible to recycle the biosolids to agriculture as an enhanced treated product.     

污水再生工艺去除病原体效果的评价

为考察常用城市污水再生回用工艺去除病毒的效果,采用柯萨奇B3型病毒(CoxB3)作为肠道病毒示踪剂进行试验.首先向污水厂二级处理出水中人工投加已知浓度的病毒,然后分别采用混凝/沉淀/过滤、超滤、氯消毒和臭氧消毒对其进行处理,并分析处理前后病毒的组织培养半数感染剂量(TCID50).结果表明,混凝/沉淀/过滤对大肠菌的去除率为2-lg～3-lg,对柯萨奇病毒的去除率约为1.83-lg;氯消毒和臭氧消毒可以有效杀灭大肠菌,在消毒剂浓度为1～10mg/L、余氯浓度为1～6 mg/L、pH为6～7的条件下,氯消毒对柯萨奇病毒的去除效果不佳,臭氧消毒对柯萨奇病毒的去除率则随臭氧浓度的不同而在1.33-lg～3.83-lg变化;超滤可有效去除大肠菌,对柯萨奇病毒的去除率为2.33-lg.     

湖北省烟草靶斑病病原鉴定及其菌丝融合群遗传分化研究

2020—2021年湖北烟区爆发新型烟草叶部病害,本研究对病原菌进行分离培养、形态观察、镜检菌丝和科赫法则验证,并提取30个菌株的DNA使用通用引物ITS1/ITS4进行rDNA-ITS序列的PCR扩增,及MEGA-X软件进行基因序列比对及系统发育树构建,同时以Rs1F2/Rs2R1为引物,进行30个菌株的rDNA-ITS基因的PCR专化性鉴定。结果表明,该病害病原菌为立枯丝核菌（Rhizoctonia solani Kühn）,30个菌株序列都隶属于R. solani AG-3融合群且均具有AG-3融合群所特有的504 bp片段。因此,确定该病害为烟草靶斑病。这是首次从湖北省烟草产区分离鉴定到该病菌。     

The importance of lactic acid bacteria for the prevention of bacterial growth and their biogenic amines formation: A review

Foodborne pathogens (FBP) represent an important threat to the consumers' health as they are able to cause different foodborne diseases. In order to eliminate the potential risk of those pathogens, lactic acid bacteria (LAB) have received a great attention in the food biotechnology sector since they play an essential function to prevent bacterial growth and reduce the biogenic amines (BAs) formation. The foodborne illnesses (diarrhea, vomiting, and abdominal pain, etc.) caused by those microbial pathogens is due to various reasons, one of them is related to the decarboxylation of available amino acids that lead to BAs production. The formation of BAs by pathogens in foods can cause the deterioration of their nutritional and sensory qualities. BAs formation can also have toxicological impacts and lead to different types of intoxications. The growth of FBP and their BAs production should be monitored and prevented to avoid such problems. LAB is capable of improving food safety by preventing foods spoilage and extending their shelf-life. LAB are utilized by the food industries to produce fermented products with their antibacterial effects as bio-preservative agents to extent their storage period and preserve their nutritive and gustative characteristics. Besides their contribution to the flavor for fermented foods, LAB secretes various antimicrobial substances including organic acids, hydrogen peroxide, and bacteriocins. Consequently, in this paper, the impact of LAB on the growth of FBP and their BAs formation in food has been reviewed extensively.     

氨基化磁珠非靶向富集食源性致病菌的条件筛选及优化

该研究基于氨基化磁珠静电富集细菌技术,建立了一种可同时富集鼠伤寒沙门氏菌,金黄色葡萄球菌,单增李斯特氏菌的方法。在每2 mL单菌液中（103 CFU/mL）分别加入5~200 μg的3种粒径的氨基化磁珠（1 μm、300 nm、100 nm）,当孵育5~90 min时检测各细菌的富集效率。将单菌液体系的富集正交试验结果应用至混和菌体系的单因素试验和正交试验,将最终结果应用至大体积实验体系以及实际样本（市售牛奶、水果沙拉）。结果表明,当氨基化磁珠添加量为50 μg、孵育时间为30 min时对3种病原菌可以达到60%以上的捕获率,所有反应均在pH值7.4的PBS中进行。磁珠粒径选择300 nm（p<0.05）。在实际样本牛奶、水果沙拉中,当三种混合菌的最低终浓度为2×102 CFU/g（mL）时,捕获率高于55%,结果可达到荧光定量PCR的检测低限。氨基化磁珠与免疫磁珠比较,其具有稳定保存、低成本,高效率等优势,其非靶向富集的能力为下游食源性致病菌的快速检测提供有效前处理富集手段。