乳酸菌抑制ACE及病原菌代谢产物研究进展

主要对乳酸菌及其发酵乳产品产生降血压的血管紧张素转换酶(ACE)抑制肽及乳酸菌消除肠道微生物降解氨基酸产生致癌因子的作用进行了阐述,表明了乳酸菌在降血压及抗癌方面具有巨大的应用前案.     

Predators indirectly control vector-borne disease: linking predator–prey and host–pathogen models

Pathogens transmitted by arthropod vectors are common in human populations, agricultural systems and natural communities. Transmission of these vector-borne pathogens depends on the population dynamics of the vector species as well as its interactions with other species within the community. In particular, predation may be sufficient to control pathogen prevalence indirectly via the vector. To examine the indirect effect of predators on vectored-pathogen dynamics, we developed a theoretical model that integrates predator–prey and host–pathogen theory. We used this model to determine whether predation can prevent pathogen persistence or alter the stability of host–pathogen dynamics. We found that, in the absence of predation, pathogen prevalence in the host increases with vector fecundity, whereas predation on the vector causes pathogen prevalence to decline, or even become extinct, with increasing vector fecundity. We also found that predation on a vector may drastically slow the initial spread of a pathogen. The predator can increase host abundance indirectly by reducing or eliminating infection in the host population. These results highlight the importance of studying interactions that, within the greater community, may alter our predictions when studying disease dynamics. From an applied perspective, these results also suggest situations where an introduced predator or the natural enemies of a vector may slow the rate of spread of an emerging vector-borne pathogen.     

噬菌体控制主要食源性致病菌的研究进展

食源性细菌疾病是当今世界上最广泛的公共卫生问题之一。由抗生素滥用导致的耐药菌株出现,以及抗生素禁用,使得人们对食源性细菌疾病的控制更加困难。噬菌体是细菌的天敌,具有感染并裂解细菌的功能,与抗生素相比,噬菌体制剂具有特异性强、自我增殖快、抗菌能力强、研发时间短等优点,因此近年来有关噬菌体作为抗菌制剂的研究受到普遍关注。本文就噬菌体在食源性病原微生物控制方面的应用研究进展作一综述,以期为噬菌体及其制剂在保障动物性食品安全领域的深入研究提供一定的参考。     

李果实贮藏期间4 株病原真菌的分离、鉴定及 碳源代谢指纹图谱分析

从采后贮藏过程中发病的“安哥诺”(Prunus angeleno)和“黑琥珀”(Prunus salicina cv. Black amber) 李果实中分离到4株丝状病原真菌。通过对病原菌株形态学特征观察以及核糖体rDNA ITS序列系统分析,确定菌株059#为串珠状赤霉(Gibberella moniliformis)、菌株067#为链格孢菌(Alternaria alternata)、菌株087#为草酸青霉(Penicillium oxalicum)以及菌株088#为塔宾曲霉(Aspergillus tubingensis)。进一步利用Biolog FF MicroPlate分析病原菌对95种碳源的利用能力,结果表明这4种病原菌的最适碳源皆在77种以上,且共同的最适碳源包括D-果糖、D-葡萄糖、蔗糖、山梨糖醇、苹果酸和柠檬酸等45种。     

鲜切果蔬中4 种病原微生物多重PCR检测技术

研发可同时检测鲜切果蔬中的单核细胞性李斯特菌、鼠伤寒沙门菌、金黄色葡萄球菌和大肠杆菌O157:H7的多重聚合酶链式反应（polymerase chain reaction,PCR）检测方法。根据单核细胞性李斯特菌inlA基因、鼠伤寒沙门菌invA基因、大肠杆菌O157:H7 wzy基因、金黄色葡萄球菌nuc基因设计及筛选出4?对引物。对多重PCR体系及条件进行优化。该方法对单核细胞性李斯特菌、鼠伤寒沙门菌、金黄色葡萄球菌和大肠杆菌O157:H7的检出限分别为3.5×106、1.6×105、2.4×105、4.8×105?CFU/mL。将优化的多重PCR方法对不同接种量富集后验证,结果表明,经过9?h富集后,该方法检出限为1?CFU/mL。该方法在鲜切莴苣、鲜切黄瓜、鲜切木瓜、鲜切哈密瓜中应用同样可扩增出4?条目标菌。因此,利用所建立的多重PCR方法对鲜切果蔬中侵染的病原菌检出限可达到1?CFU/g。该方法相较于传统的培养检测方法具有节约大量的劳力、试剂、时间等优点,检测时间也由原来的5～7?d缩短至9～11?h,对于企业或分析检验中心大批量样品的监测具有指导意义。     

Pathogen-specific production losses in bovine mastitis

Reduction in long-term milk yields represents a notable share of the economic losses caused by bovine mastitis. Efficient, economic, and safe measures to prevent these losses require knowledge of the causal agent of the disease. The aim of this study was to investigate pathogen-specific impacts of mastitis on milk production of dairy cows. The materials consisted of milk and health recording data and microbiological diagnoses of mastitic quarter milk samples of 20,234 Finnish dairy cows during 2010, 2011, and 2012. The 6 most common udder pathogens were included in the study: Staphylococcus aureus, non-aureus staphylococci (NAS), Escherichia coli, Corynebacterium bovis, Streptococcus uberis, and Streptococcus dysgalactiae. We used a 2-level multilevel model to estimate curves for lactations with and without mastitis. The data on lactation periods to be compared were collected from the same cow. To enable comparison among lactations representing diverse parities, the estimated lactation curves were adjusted to describe the cow's third lactation. Mastitis caused by each pathogen resulted in milk production loss. The extent of the reduction depended on the pathogen, the timing of mastitis during lactation, and the type of mastitis (clinical vs. subclinical). The 2 most commonly detected pathogens were NAS and Staph. aureus. Escherichia coli clinical mastitis diagnosed before peak lactation caused the largest loss, 10.6% of the 305-d milk yield (3.5 kg/d). The corresponding loss for Staph. aureus mastitis was 7.1% (2.3 kg/d). In Staph. aureus mastitis diagnosed between 54 and 120 d in milk, the loss was 4.3% (1.4 kg/d). The loss was almost equal in both clinical and subclinical mastitis caused by Staph. aureus. Mastitis caused by Strep. uberis and Strep. dysgalactiae resulted in losses ranging from 3.7% (1.2 kg/d) to 6.6% (2.1 kg/d) depending on type and timing of mastitis. Clinical mastitis caused by the minor pathogens C. bovis and NAS also had a negative effect on milk production: 7.4% (2.4 kg/d) in C. bovis and 5.7% (1.8 kg/d) in NAS when both were diagnosed before peak lactation. In conclusion, minor pathogens should not be underestimated as a cause of milk yield reduction. On single dairy farms, control of E. coli mastitis would bring about a significant increase in milk production. Reducing Staph. aureus mastitis is the greatest challenge for the Finnish dairy sector.     

Recent developments in nanotechnology transforming the agricultural sector: a transition replete with opportunities

The applications and benefits of nanotechnology in the agricultural sector have attracted considerable attention, particularly in the invention of unique nanopesticides and nanofertilisers. The contemporary developments in nanotechnology are acknowledged and the most significant opportunities awaiting the agriculture sector from the recent scientific and technical literature are addressed. This review discusses the significance of recent trends in nanomaterial‐based sensors available for the sustainable management of agricultural soil, as well as the role of nanotechnology in detection and protection against plant pathogens, and for food quality and safety. Novel nanosensors have been reported for primary applications in improving crop practices, food quality, and packaging methods, thus will change the agricultural sector for potentially better and healthier food products. Nanotechnology is well‐known to play a significant role in the effective management of phytopathogens, nutrient utilisation, controlled release of pesticides, and fertilisers. Research and scientific gaps to be overcome and fundamental questions have been addressed to fuel active development and application of nanotechnology. Together, nanoscience, nanoengineering, and nanotechnology offer a plethora of opportunities, proving a viable alternative in the agriculture and food processing sector, by providing a novel and advanced solutions. © 2017 Society of Chemical Industry     

Enhanced phagocytosis of Aggregatibacter actinomycetemcomitans cells by macrophages activated by a probiotic Lactobacillus strain

The activation of phagocytosis is one important approach to clearing pathogenic cells in a host. This study evaluated the ability of probiotic lactobacilli to induce phagocytic activity as well as the clearance of a periodontal pathogen, Aggregatibacter actinomycetemcomitans. First, the activation of phagocytosis was found by using lyophilized dead cells. Probiotic Lactobacillus strains significantly enhanced the phagocytic activity of macrophage cells, indicating that the probiotic lactobacilli have a remarkable ability to stimulate the macrophages. Essentially, 3 Lactobacillus strains tested did not have any critical toxic effect on the murine macrophage, and Lactobacillus johnsonii NBRC 13952 showed the least cytotoxic effect on the RAW264.7 macrophages. The expression of classically activated macrophage markers, IL-1β, and cluster of differentiation 80 increased by L. johnsonii NBRC 13952; however, there was no significant difference for IL-18. The highest phagocytic activity by macrophages was found in a condition in which the macrophage activated by L. johnsonii NBRC 13952 functions to kill the cells of A. actinomycetemcomitans. Correlating with the result, a high amount of hypodiploid DNA (SubG1) was detected from the macrophage cells stimulated by L. johnsonii NBRC 13952. Taken together, the results suggest that macrophages activated by the Lactobacillus strain can facilitate the phagocytosis of A. actinomycetemcomitans cells by linking with enhanced apoptotic activities. In conclusion, L. johnsonii NBRC 13952 has a certain role in activating the RAW264.7 macrophages, thereby counteracting the infection of A. actinomycetemcomitans.     

Salmonella and Campylobacter biofilm formation: a comparative assessment from farm to fork

It takes several steps to bring food from the farm to the fork (dining table), and contamination with food‐borne pathogens can occur at any point in the process. Campylobacter spp. and Salmonella spp. are the main microorganisms responsible for foodborne disease in the EU. These two pathogens are able to persist throughout the food supply chain thanks to their ability to form biofilms. Owing to the high prevalence of Salmonella and especially of Campylobacter in the food supply chain and the huge efforts of food authorities to reduce these levels, it is of great importance to fully understand their mechanisms of persistence. Diverse studies have evaluated the biofilm‐forming capacity of foodborne pathogens isolated at different steps of food production. Nonetheless, the principal obstacle of these studies is to reproduce the real conditions that microorganisms encounter in the food supply chain. While there are a wide number of Salmonella biofilm studies, information on Campylobacter biofilms is still limited. A comparison between the two microorganisms could help to develop new research in the field of Campylobacter biofilms. Therefore, this review evaluates relevant work in the field of Salmonella and Campylobacter biofilms and the applicability of the data obtained from these studies to real working conditions. © 2018 Society of Chemical Industry     

多重PCR法检测鲜切哈密瓜中3种食源性致病菌

建立可同时检测鲜切哈密瓜中的单增李斯特菌、鼠伤寒沙门氏菌和大肠杆菌O157:H7的多重聚合酶链式反应(polymerase chain reaction,PCR)检测方法。根据单增李斯特菌inl A基因、鼠伤寒沙门氏菌inv A基因、大肠杆菌O157:H7的wzy基因设计3对特异性引物。对多重PCR反应体系中的引物浓度、退火温度、Mg2+浓度、d NTP浓度进行了优化,并确定适宜的多重PCR反应体系及反应条件。结果表明:25μL反应体系,10×PCR buffer为2.5μL,Mg Cl2(25 mmol/L)为3.5μL,d NTPs(2.5 mmol/L)为2μL,inl A基因上下游引物(5μmol/L)为1μL,inv A基因上下游引物(5μmol/L)为1μL,wzy基因上下游引物(5μmol/L)为2μL,单增李斯特菌DNA模板为1μL,鼠伤寒沙门氏菌DNA模板为1μL,大肠杆菌O157:H7 DNA模板为1μL,ex Taq DNA聚合酶(5 U/L)为0.3μL,加dd H2O补足25μL。反应条件为95℃预变性3 min;94℃变性30 s,53.9℃退火30 s,72℃延伸30 s,32个循环;72℃延伸10 min。鲜切哈密瓜中人工接种的目标菌的灵敏度为单增李斯特菌2.7×104 CFU/g,大肠杆菌O157:H7 3.3×104 CFU/g以及鼠伤寒沙门氏菌3.8×104 CFU/g。该技术可为快速检测鲜切哈密瓜中病原菌污染度及其控制提供参考依据。