基于NMR纳米探针的生物传感器用于快速检测沙门氏菌

通过将沙门氏菌单抗与羧基磁珠偶联制备免疫磁珠,并以此为NMR分子探针,以免疫磁珠为生物传感器,特异性地捕获并检测出样品中的致病菌,从而建立一种更快的检测沙门氏菌的方法。实验将得到的不同样品溶液放入核磁共振仪中检测自旋-自旋弛豫时间（T2）值,考察不同条件对T2值的影响。通过实验发现,免疫磁珠的使用量,缓冲溶液的选择,捕获时间的长短都会对样品T2值产生影响。通过优化实验,分别绘制出不同条件下T2值的曲线变化,并得出最佳捕获条件。在捕获缓冲溶液为磷酸盐缓冲溶液PBS（0.01 mol/L,p H7.4）,免疫磁珠使用量为50μg,混匀捕获时间为1.5 h的条件下,核磁共振仪测得的样品T2值曲线最佳。其检测线性范围为10⁴¹0⁷CFU/m L。本研究为沙门氏菌的检测提供了新的方法和途径,缩短了检测时间和工序,并且为低场核磁共振技术研究应用开辟了广阔的空间。      

Inhibition of Bacterial Pathogens in Medium and on Spinach Leaf Surfaces using Plant‐Derived Antimicrobials Loaded in Surfactant Micelles

Encapsulation of hydrophobic plant essential oil components (EOC) into surfactant micelles can assist the decontamination of fresh produce surfaces from bacterial pathogens during postharvest washing. Loading of eugenol and carvacrol into surfactant micelles of polysorbate 20 (Tween 20), Surfynol® 485W, sodium dodecyl sulfate (SDS), and CytoGuard® LA 20 (CG20) was determined by identification of the EOC/surfactant‐specific maximum additive concentration (MAC). Rheological behavior of dilute EOC‐containing micelles was then tested to determine micelle tolerance to shearing. Antimicrobial efficacy of EOC micelles against Escherichia coli O157:H7 and Salmonella enterica serotype Saintpaul was first evaluated by the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Pathogen‐inoculated spinach was treated with eugenol‐containing micelles applied via spraying or immersion methods. SDS micelles produced the highest MACs for EOCs, while Tween 20 loaded the lowest amount of EOCs. Micelles demonstrated Newtonian behavior in response to shearing. SDS and CG20‐derived micelles containing EOCs produced the lowest MICs and MBCs for pathogens. E. coli O157:H7 and S. Saintpaul were reduced on spinach surfaces by application of eugenol micelles, though no differences in numbers of surviving pathogens were observed when methods of antimicrobial micelle application (spraying, immersion) was compared (P ≥ 0.05). Data suggest eugenol in SDS and CG20 micelles may be useful for produce surface decontamination from bacterial pathogens during postharvest washing.     

沙门氏菌的依赖于核酸序列恒温扩增检测方法的建立

采用自行建立和优化的依赖于核酸序列恒温扩增(nucleic acid sequence-based amplification,NASBA)检测体系,对沙门氏菌进行检测。采用沙门氏菌的invA基因为目的片段设计特异性引物,建成可快速检测沙门氏菌的NAS-BA检测法,并进行了特异性和灵敏度试验。结果表明:所建立起的NASBA检测方法,灵敏度为7.1×102cfu/ml,高于普通PCR方法。     

Prevalence,Distribution, and Diversity of Salmonella spp. in Meat Samples Collected from Italian Slaughterhouses

Recently worldwide food safety authorities indicated the rise of foodborne outbreaks linked to Salmonella: this highlighted the need to intensify monitoring and apply more targeted controls to help manage the spread of the disease. The aim of this study was to assess the prevalence and distribution of Salmonella serotypes in 7 slaughterhouses, located in different areas of Naples province (Regione Campania, Italy). Meat samples collected from the slaughterhouses were submitted for standardized microbiological analysis in 2015. Results of routine testing for Salmonella spp. were analyzed and then compared to biochemical and molecular evaluations. Salmonella spp. were detected in 12% of 320 samples examined (39/320) and the isolation rates ranged from 87% (32 samples) for raw poultry meat to 13% (7 samples) for pork meat. Biochemical serotyping showed that approximately 50% of the isolates belonged to Salmonella enterica serotype Choleraesuis. Rapid detection methods, such as molecular analysis (polymerase chain reaction and gel electrophoresis), able to confirm food matrices contamination, represent a valid support to the fast identification of Salmonella species. A further aspect of the study consisted, indeed, on analyzing isolated strains through molecular evaluations. By amplifying bacterial DNA—using invA primers, selective for Salmonella—it was possible, in less than 3 h, to classify the isolates as Salmonella spp., confirming the results of microbiological outcomes. Results of distribution analysis, supported by rapid molecular approaches, showed the difficulty of reducing Salmonella risk on food chain. This emphasized the importance of periodic surveillance to prevent outbreaks.     

Engineering a Novel Bivalent Oral Vaccine against Enteric Fever

Enteric fever is a major global healthcare issue caused largely by Salmonella enterica serovars Typhi and Paratyphi A. The objective of this study was to develop a novel, bivalent oral vaccine capable of protecting against both serovars. Our approach centred on genetically engineering the attenuated S. Typhi ZH9 strain, which has an excellent safety record in clinical trials, to introduce two S. Paratyphi A immunogenic elements: flagellin H:a and lipopolysaccharide (LPS) O:2. We first replaced the native S. Typhi fliC gene encoding flagellin with the highly homologous fliC gene from S. Paratyphi A using Xer-cise technology. Next, we replaced the S. Typhi rfbE gene encoding tyvelose epimerase with a spacer sequence to enable the sustained expression of O:2 LPS and prevent its conversion to O:9 through tyvelose epimerase activity. The resulting new strain, ZH9PA, incorporated these two genetic changes and exhibited comparable growth kinetics to the parental ZH9 strain. A formulation containing both ZH9 and ZH9PA strains together constitutes a new bivalent vaccine candidate that targets both S. Typhi and S. Paratyphi A antigens to address a major global healthcare gap for enteric fever prophylaxis. This vaccine is now being tested in a Phase I clinical trial ({"type":"clinical-trial","attrs":{"text":"NCT04349553","term_id":"NCT04349553"}}NCT04349553).     

滤纸搭桥法在食品检验中对沙门菌血清型鉴定的应用探究

本试验用滤纸搭桥法对食品中分离出的沙门菌做进一步的血清型鉴定.结果表明:滤纸条搭桥法与简易平板法相比较,耗时更短,简易平板法普遍要传1?2代后再进行血清分型,而滤纸条搭桥法可直接接种血平板诱导培养后进行血清分型,且对沙门菌的鞭毛抗原诱导效果更佳,血清分型结果更为准确.在实际食品检验工作中可以把滤纸条搭桥法作为国家标准G...     

ELISA方法与国标法在检测鲜奶中沙门氏菌的比较研究

应用直接ＥＬＩＳＡ方法对３５０份奶样进行沙门氏菌的检测，其阳性检出率为１．４％；同时采用常规方法检测，其阳性检测率为１．２％。与常规方法相比，该法的敏感性和特异性分别为１００％和９９．７％（３５０份奶样）。结果表明，该法具有快速、准确等特点，２￣３天即可完成样品筛选。     

Utilizing Acidic Sprays for Eliminating Salmonella enterica on Raw Almonds

ABSTRACT In‐shell or shelled almonds inoculated with Salmonella were sprayed with water, acetic acid, citric acid, acidified sodium chlorite, peroxyacetic acid, or a mixture of citric, hydrochloric, and phosphoric acids before testing for Salmonella on xylose‐lysine‐deoxycholate (XLD) agar and tryptic soy agar (TSA). Spraying acids on in‐shell almonds reduced about 0.48 to 1.88 and 0.22 to 0.67 log colony‐forming units (CFU)/g of Salmonella on XLD agar and TSA counts, respectively, on the in‐shell almonds but had no effect on the edible portion of the almonds (shelled almonds). When spraying acids on shelled almonds, a single spray application (1.6 mL acid solution/25 g of shelled almonds) with 1 min holding caused 0.72 to 1.93 and 0.38 to 1.35 log CFU/ g reductions of Salmonella counts on XLD agar and TSA, respectively. Increasing the holding time to 5 min did not enhance the reductions. When spraying shelled almonds, increasing the number of application (1 to 3 times) enhanced Salmonella reduction. Except for the peroxyacetic acids, increasing total holding time (5 to 120 min) improved the efficacies. Furthermore, increasing acid concentrations improved the efficacies of acetic, citric, and peroxyacetic acid treatments. Estimated 5‐log reductions on both TSA and XLD counts can be achieved under laboratory conditions using 10% citric acid by (1) the combination of shelling, 1 spraying, and 3 d of storage, (2) the combination of shelling, 2 sprayings, and 1 d of storage, or (3) the combination of shelling and 3 sprayings. Acidic sprays may be utilized for enhancing the microbiological safety of raw nuts.