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).     

食品中3种致病菌快速检测方法的研究进展

总结食品中沙门氏菌、副溶血性弧菌和单核细胞增生李斯特菌3种致病菌的快速检测方法。传统的细菌学检测耗时繁琐,不能满足当今发展的需求。目前采用的PCR、ELISA、核酸杂交、生物传感器等分子生物学和免疫学等技术,检测周期短、精确度高、特异性和敏感性好等,这些方法联用能达到更好的检测效果。     

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。     

一起伦敦沙门氏菌食物中毒分离株的病原特征分析

目的 分析2020年广州市一起伦敦沙门氏菌食物中毒分离株的病原特征。方法 对分离纯化的10株沙门氏菌进行血清型鉴定,耐药检测,毒力岛(salmonella pathogenicity island,SPI)基因片段SPI-1、SPI-2、SPI-3、SPI-4、SPI-5的PCR检测及脉冲场凝胶电泳(pulsed-field gel electrophoresis,PFGE)分析。结果 10株沙门氏菌血清型鉴定抗原式均为O₁₀：l、v：1、6,即伦敦沙门氏菌,药敏试验显示10株沙门氏菌对氨苄西林(AMP)、萘啶酸(NAL)、头孢唑林(CFZ)、复方磺胺(SXT)、氨苄西林／舒巴坦(AMS)100 %耐药,对头孢噻肟(CTX)、头孢西丁(CFX)、头孢他啶(CAZ)、亚胺培南(IPM)、庆大霉素(GEN)、四环素(TET)、氯霉素(CHL)、环丙沙星(CIP)100 %敏感。毒力岛基因SPI-1~SPI-5全部为阳性。PFGE聚类分析显示,5株病患株、3株食品株、2株环境株为高度同源株。结论 引起此次食物中毒事件的病原菌是伦敦沙门氏菌,应进一步加强餐饮环节的卫生监测和控制。     

基于核酸适体微球的沙门氏菌检测方法研究

目的:研究基于核酸适体的微球芯片系统应用于沙门氏菌检测的可行性。方法:采用偶联有沙门氏菌适体的微球作为载体,以荧光作为检测信号建立微球芯片体系,并优化影响检测结果的各项因素。结果:通过此方法检测20份水产样品,6份检出沙门氏菌,检出率为30%。结论:建立的检测体系能实现对沙门氏菌的快速,准确的检测,且具有较高的特异性。