肠炎沙门菌rfbG基因缺失株的构建及其生物学特性研究

目的 探究rfbG基因对肠炎沙门菌毒力的影响,评价肠炎沙门菌缺失rfbG基因后作为减毒活疫苗的潜力。方法 利用自杀质粒介导的同源重组技术,无痕构建肠炎沙门菌Z11ΔrfbG缺失株,并对其生物学特性进行分析。结果 成功构建肠炎沙门菌Z11ΔrfbG缺失株,与野生株相比,缺失株Z11ΔrfbG生化特性没有发生变化,在LB液体培养基中生长速率较慢;缺失株生物被膜形成能力显著弱于野生株,其感染J774A.1细胞后,产生的细胞毒性亦显著低于野生株。此外,缺失株可与吖啶橙溶液发生凝集,但与O₉血清不发生凝集。结论 rfbG基因缺失显著降低了肠炎沙门菌Z11的毒力,且缺失株符合粗糙型菌株的特点,Z11ΔrfbG不仅具有作为沙门菌减毒活疫苗或载体的潜质,也具有作为DIVA疫苗的潜力,为肠炎沙门菌减毒活疫苗的开发研究奠定了基础。     

龙岩市239株沙门菌毒力基因检测结果分析

目的 了解龙岩市沙门菌毒力基因携带与变迁情况,为沙门菌病的防制提供理论依据。方法 对1991-2017年间收集的分离自人体与食品样本的239株沙门菌进行复核鉴定,并用PCR方法检测invA、sopB、sifA、sscA、sseE、spvB、spvC、spvR、pefA等9个沙门菌毒力基因的片段。结果 龙岩市沙门菌以肠炎沙门菌和鼠伤寒沙门菌为主,占62.3%(149/239),属于SPI1的invA、sopB毒力基因检出率为100%,属于SPI2的sseE、sscA、sifA毒力基因的检出率分别为99.2%、95.0%、85.4%,毒力质粒基因spvC检出率71.1%,pefA、spvB、spvR检出率均为46.4%。并且其携带数量也随着时间的进程而显著增加;肠炎沙门菌质粒毒力基因携带率显著高于鼠伤寒沙门菌。肠炎沙门菌以检出全部9种毒力基因为主,占83.5%(76/91);鼠伤寒沙门菌以invA、sopB、sseE、sscA、sifA阳性,spvB、spvR、pefA阴性结果多见,占77.6%(45/58)。人体与食品样本来源的沙门菌所携带毒力基因数量没有差异。结论 龙岩市沙门菌携带毒力基因数量较多,毒力较强,质粒毒力基因随着时间的进程而累积,人源性与食源性沙门菌交叉污染严重,必须加强人、禽、畜沙门菌病的监测与管理。     

兰州地区腹泻患儿沙门菌耐药性与分子分型分析

目的 了解兰州地区腹泻患儿沙门菌的血清型分布特征,耐药状况及分子分型特征,为儿童沙门菌感染的防治提供依据。方法 2018-2020年收集兰州地区哨点医院腹泻患儿粪便标本中分离的149株沙门菌菌株进行血清学分型、药物敏感试验和脉冲场电泳分型。结果 腹泻患儿感染沙门菌以夏秋季为主,1~3岁幼儿居多,占59.73%。149株沙门菌分为33个血清型,其中肠炎沙门菌和鼠伤寒沙门菌为优势血清型,分别占30.87%和28.19%。沙门菌对氨苄西林耐药率最高为79.87%,多重耐药率为78.52%,其中鼠伤寒沙门菌和肠炎沙门菌多重耐药率分别为80.95%、76.09%。经PFGE分子分型将肠炎沙门菌分为20个带型,包含2株及以上的带型有6种;鼠伤寒沙门菌分为30个带型,ST1带型包含2株菌。结论 兰州市腹泻患儿中沙门菌以非伤寒沙门菌为主,耐药率呈上升趋势,多重耐药严重,肠炎沙门菌PFGE分型同源性较高,鼠伤寒沙门菌带型呈多样性分布。     

肠炎沙门菌sifA基因缺失株的无痕构建及其在巨噬细胞内的增殖特性研究

目的 本研究旨在探究sifA基因对肠炎沙门菌胞内寄生和增殖的影响,以探索肠炎沙门菌的致病机理。方法 根据同源重组原理,无痕构建肠炎沙门菌C50041的sifA基因缺失株,通过蓝白斑、抗生素耐药性、PCR和基因测序方法对基因缺失株进行鉴定,并从生物学特性、胞内沙门菌增殖、sifA基因在胞内外菌中表达等方面,分析sifA基因对肠炎沙门菌的影响。结果 成功构建肠炎沙门菌C50041ΔsifA,蓝白斑、抗生素耐药性、PCR和基因测序方法证明该菌株是正确的。其生长速度和生化特性没有发生改变。ΔsifA株感染巨噬细胞后,其胞内沙门菌量显著少于其野生株。sifA基因在spiC基因缺失株中表达量增加。结论 肠炎沙门菌C50041ΔsifA被成功构建,其在巨噬细胞内的增殖量显著降低,sifA基因表达可能受spiC基因调控,本研究为深入探究肠炎沙门菌在细胞内增殖及sifA基因的功能奠定基础。     

成都市人源沙门菌基因组特征分析

目的 基于全基因组测序技术,探究成都市人源沙门菌的基因组特征, 为监测与预防沙门菌感染提供资料。方法 收集35株成都市人源沙门菌(分离自腹泻患者粪便)进行全基因组测序。根据测序数据,进行血清型预测、耐药基因及可移动遗传元件预测、毒力因子注释及分布分析。结果 35株沙门菌分离株经全基因组测序,共预测到5种血清型,包括15株I 4,[5],12:i:-沙门菌(13株为ST34、2株为新ST型)、12株鼠伤寒沙门菌(ST19)、5株肠炎沙门菌(ST11)、2株德比沙门菌(ST40)与1株火鸡沙门菌(ST463)。35株沙门菌分离株共预测到10类42种不同的耐药基因,其中氨基糖苷类aac(6')-Iaa携带率为100%(35/35)。I 4,[5],12:i:-沙门菌的耐药基因、质粒及插入序列数目及种类多于其他血清型菌株。I 4,[5],12:i:-、鼠伤寒沙门菌和肠炎沙门菌的毒力因子数目大于其他血清型菌株。部分鼠伤寒沙门菌有更高的毒力质粒、质粒编码菌毛和血清抗性毒力因子分布。结论 成都市人源沙门菌不同血清型菌株之间耐药基因、可移动遗传元件、毒力因子分布差异明显,值得在转录组、蛋白组进一步探究其耐药与毒力机制。     

30株水禽沙门菌的分离鉴定与血清型分析

目的 通过分析佛山及其周边地区水禽沙门菌感染的血清型分布特征,为防控水禽沙门菌病与制定公共卫生安全措施提供参考信息。方法 本试验对发病水禽采用细菌分离纯化、生化特性鉴定、PCR方法鉴定获得30株水禽沙门菌,以玻片凝集反应法作血清型鉴定。结果 30株水禽沙门菌的血清型含4(B、D、C₁、E₁ )个群别7种血清型,B群有25株沙门菌分离株,包括19株鼠伤寒沙门菌(S.Typhimurium)、3株乙型副伤寒沙门菌(S.Paratyhi)、2株印第安纳沙门菌(S.Indiana)、1株斯坦利沙门菌(S.Stanley);D群有肠炎沙门菌(S.Enteritidis)1株;C1群有2株波茨坦沙门菌(S.Potsdam);E₁群有2株明斯特沙门菌(S.Muenster)。结论 30株水禽沙门菌分离株均为人兽共患血清型,其中B群鼠伤寒沙门菌为优势血清型,对于水禽感染沙门菌病的防控,应优先考虑鼠伤寒沙门菌感染。     

2010-2018年安徽省马鞍山市腹泻患者中非伤寒沙门菌的分子分型与耐药性研究

目的 了解马鞍山地区腹泻监测人群非伤寒沙门菌的感染状况、血清学分布、分子分型与耐药性等特征。方法 对2010-2018年腹泻患者中分离的非伤寒沙门菌进行血清学分型、脉冲场凝胶电泳(PFGE)和药物敏感性试验。结果 从2 998例腹泻患者中检出非伤寒沙门菌腹泻263例(8.8%),其中2例为2种非伤寒沙门菌混合感染;6-7月份非伤寒沙门菌感染率较高,05岁年龄组感染率最高(15.9%)(χ²=72.98,P<0.001);265株非伤寒沙门菌分为36个血清型,优势血清型为阿贡纳沙门菌、肠炎沙门菌和鼠伤寒沙门菌;阿贡纳沙门菌的PFGE带型分布较集中,有菌株成簇存在的现象;测试菌株总耐药率为95.6%(66/69),多重耐药率为82.6%(57/69);测试菌株对AMP(79.7%)、STR(75.3%)和Sul(66.6%)耐药率较高,对AMI和AZI 完全敏感;发现2株ESBLs的菌株,均为多重耐药菌株;鼠伤寒沙门菌和肠炎沙门菌对不同药物的敏感性有所不同,前者对喹诺酮类药物较敏感,而后者对四环素类药物较敏感。结论 马鞍山地区优势血清型为阿贡纳沙门菌,与其他地区不同。阿贡纳沙门菌有成簇存在的情况,提示有既往暴发的可能。总耐药及多重耐药现象严重,应谨慎用药并加强对病例的耐药监测。     

2013-2014年贵阳市感染性腹泻监测病例中沙门菌的病原学监测分析

目的 了解2013-2014年贵阳市腹泻监测病例中沙门菌的血清型别分布及脉冲场凝胶电泳(Pulse-Field Gel Electrophoresis,PFGE)分型特征,为贵阳市沙门菌病的防控提供科学依据。方法 收集2013-2014年贵阳市4家哨点医院感染性腹泻病例的432份粪便标本,对其进行沙门菌的分离培养、生化鉴定、血清分型及PFGE分型。结果 432例感染性腹泻患者的粪便标本共检出沙门菌35株,检出率为8.10%(35/432),男女检出之比为1.5:1,发病年龄主要集中在0~5岁;各季度间沙门菌检出率经Fisher确切概率法比较无统计学差异(P=0.052)。35株沙门菌分成9种血清型,其中优势血清型为肠炎沙门菌11株(占31.43%)和鼠伤寒沙门菌9株(占25.71%),其次克勒肯威尔沙门菌6株(占17.14%),斯坦利沙门菌3株,德尔卑沙门菌2株,阿贡纳沙门菌、婴儿沙门菌和病牛沙门菌血清型各1株,1株未分型。经XbaⅠ酶切后11株肠炎沙门菌分成8种PFGE型,优势型为JEGX01.CN0007;9株鼠伤寒沙门菌分成9种PFGE型,总体型别呈多样性分布。结论 贵阳市引起感染性腹泻的沙门菌以肠炎沙门菌和鼠伤寒沙门菌为主,PFGE型别呈多样性。     

深圳市腹泻患者沙门菌感染状况和耐药性分析

目的 分析2014-2017年深圳地区腹泻患者沙门菌的感染特征和耐药性情况,为沙门菌感染的防控提供科学依据。方法 从深圳市3家哨点医院腹泻门诊收集患者粪便标本,进行沙门菌的分离鉴定、血清分型及药敏试验;对7家医院上送的住院病人分离的沙门菌进行血清分型和药敏试验。结果 4 847份门诊患者的粪便标本中,分离出192株沙门菌,检出率为4.0%。5-10月是沙门菌检出的高峰, 5岁以下儿童和6-17岁是感染的主要人群,检出率分别为6.2%和5.3%。192株沙门菌中鉴定出18种血清型,其中鼠伤寒沙门氏菌、鼠伤寒沙门氏菌变种和肠炎沙门氏菌是最常见的3种血清型,另有19株未能分型。77株住院病人分离的沙门菌中鉴定出20种血清型,其中肠炎沙门氏菌、鼠伤寒沙门氏菌变种、甲型副伤寒沙门氏菌占比分别为33.8%、13.0%和11.7%,另有3株未能分型。45株沙门菌对氨苄西林、环丙沙星和左旋氧氟沙星的耐药最为严重,自2015年开始出现对喹诺酮类药物的耐药和多重耐药菌株,10株鼠伤寒沙门氏菌中多重耐药率为50.0%。结论 深圳市腹泻患者的沙门菌感染以17岁以下儿童为主,5-10月份为感染的高峰期,沙门菌的血清型分散,其中肠炎沙门氏菌和鼠伤寒沙门氏菌、鼠伤寒沙门氏菌变种是主要的血清型,多重耐药自2015年开始日趋严重,临床上应合理规范用药并且加强耐药监测。     

河南省人源产ESBLs鼠伤寒沙门菌单相变异株的分子特征研究

目的 分析河南省腹泻病例粪便标本中产超广谱β内酰胺酶(ESBLs) 的鼠伤寒沙门菌单相变异株耐药情况,并研究其分子学特征。方法 对河南省腹泻粪便中分离的124株鼠伤寒沙门菌单相变异株沙门菌,通过肉汤稀释法进行抗生素敏感性试验并筛选产ESBLs菌株;PCR方法检测β-内酰胺酶编码基因携带情况,采用质粒接合试验分析耐药基因的水平转移情况,应用脉冲场凝胶电泳(PFGE)进行亲缘关系分析。结果 124株鼠伤寒沙门菌单相变异株沙门菌耐药严重,其中有16株为产ESBLs菌株。16株产ESBLs菌株均携带CTX-M型耐药基因,并检测出OXA型和TEM型耐药基因;其中9株菌可将CTX-M基因通过质粒转移到大肠埃希菌J53,药敏分析发现其他抗生素的耐药性可以发生共转移。16株产ESBLs 鼠伤寒沙门菌单相变异株沙门菌经XbaⅠ酶切后共分为14种带型,无明显的优势带型。结论 检出产ESBLs 的鼠伤寒沙门菌单相变异株沙门菌基因型具有多样性,耐药基因可通过接合性质粒在不同菌属间播散。     

肠炎沙门菌ΔspiCΔcrp基因工程疫苗候选株的构建

目的 构建肠炎沙门菌ΔspiCΔcrp双基因缺失株,以探索其作为新型基因工程疫苗的可能性。方法 以等位基因同源重组方法,在构建单基因缺失肠炎沙门菌ΔspiC基础上,运用λRed重组酶系统构建双基因缺失株肠炎沙门菌ΔspiCΔcrp。结果 PCR和抗生素抗性结果表明肠炎沙门菌ΔspiCΔcrp成功构建;生物学鉴定显示,与野生菌相比,其生长速度与生化特性发生了变化,LD₅₀提高约1 000倍,毒力显著降低。结论 双基因缺失株肠炎沙门菌ΔspiCΔcrp被成功构建,为其作为疫苗的免疫学评价奠定基础。     

无锡市腹泻病人沙门菌的病原学特征及分子分型研究

目的分析无锡市腹泻人群中分离的沙门菌的流行特征;同时比较主要血清型菌株间的脉冲场凝胶电泳(PFGE)带型差异,为沙门菌感染的防控提供实验数据。方法收集2015年无锡市腹泻病人的粪便标本,分别进行沙门菌的分离鉴定、药敏试验、血清型分型以及PFGE分型分析。结果 756份粪便标本中共分离到32株沙门菌,阳性率为4.23%;检出时间主要集中在5~10月份,感染人群以老年人为主。药敏试验说明无锡地区的沙门菌对氨苄西林的耐药率最高,达56.25%;对环丙沙星和头孢他啶的耐药率最低,均为6.25%。32株沙门菌共鉴定出11种血清型,以肠炎沙门菌和鼠伤寒沙门菌为主,分别占31.25%和21.88%。对这2种血清型的沙门菌进行PFGE分析,显示肠炎沙门菌所有带型的相似度均在85%以上,鼠伤寒沙门菌的带型各不相同。结论无锡市沙门菌的感染具有明显季节和年龄分布差异性,流行的优势血清型为肠炎沙门菌。无锡市需同时加强对食品和环境中沙门菌的监测。     

Drug resistance of Salmonella strains isolated from community infections in Ankara, Turkey, 1993-99.

160 Salmonella strains were isolated from children at the paediatrics department of Ankara University. 48.1% of the isolates were Salmonella enteritidis, 41.9% Salmonella typhimurium and 10% other serotypes. For the analysis of data, the study period was divided into 2 periods: 1993-95 and 1996-99. A decline in the isolation rate of S. typhimurium (from 63.1% to 30.1%) and rapid rise in S. enteritidis (from 31.6% to 57.3) was observed during the review period. However, for S. typhimurium isolates, the 5-drug (ampicillin, chloramphenicol, streptomycin, tetracycline and sulfonamides) pattern of resistance was increased from 13.5% to 38.7% in the second period. Since S. enteritidis and 5-drug-resistant S. typhimurium have also increased in other countries, their pandemic spread in humans indicates the continuing importation and exportation of these pathogens.     

O-antigenic specificity of the protective supernatant factor from Salmonella typhimuvium effective in S. typhimurium-infected mice

A supernatant factor (SF) prepared from cultures of Salmonella typhimurium protected naturally susceptible inbred mice against challenge with S. typhimurium subcutaneously injected (s.c.i.), but not against Salmonella enteritidis, suggesting tha the relevant specificity involved lipopolysaccharide. Further experiments were performed with two transductant strains of S. typhimurium. Strain SH6701 has O-antigen 4 from S. typhimurium and SH6703 had O-antigen 9 from S. enteritidis. Immunization with SF from SH6701 protected 95% BALB/c mice challenged with 100 LD50 S. typhimurium s.c.i., whereas SH6703 immunization had no effect on survival or mean survival time. SH 6703 SF gave some protection against homologous challenge. Antibody titres and delayed-type hypersensitivity reactions were also tested in immunized mice. The SF was, therefore, specific in that O-antigen 4 was necessary to protect mice against S. typhimurium challenge. Since we have previously demonstrated protein to be necessary for protection by SF, the active factor may be in the form of a protein-lipopolysaccharide complex.     

Phase variation of the lpf operon is a mechanism to evade cross-immunity between Salmonella serotypes

Conventional wisdom holds that phase variation is a mechanism for immune evasion. However, despite fimbrial phase variation, mice previously exposed to Salmonella typhimurium are protected against a subsequent challenge. We evaluated whether lpf phase variation instead may be a mechanism to evade cross-immunity between Salmonella serotypes. Mice were immunized orally with S. typhimurium aroA mutants either that expressed the lpf operon (phase-on variant) or in which the entire lpf operon had been removed by deletion. During a subsequent challenge with virulent Salmonella enteritidis a selection against lpf phase-on variants was observed in mice previously exposed to S. typhimurium long polar fimbriae. Vaccination with S. typhimurium did not confer protection against challenge with S. enteritidis, presumably because lpf phase-off variants were able to evade cross-immunity. We propose that lpf phase variation is a mechanism to evade cross-immunity between Salmonella serotypes, thereby allowing their coexistence in a host population.     

A role for Salmonella fimbriae in intraperitoneal infections

Enteric bacteria possess multiple fimbriae, many of which play critical roles in attachment to epithelial cell surfaces. SEF14 fimbriae are only found in Salmonella enterica serovar Enteritidis (S. enteritidis) and closely related serovars, suggesting that SEF14 fimbriae may affect serovar-specific virulence traits. Despite evidence that SEF14 fimbriae are expressed by S. enteritidis in vivo, previous studies showed that SEF14 fimbriae do not mediate adhesion to the intestinal epithelium. Therefore, we tested whether SEF14 fimbriae are required for virulence at a stage in infection after the bacteria have passed the intestinal barrier. Polar mutations that disrupt the entire sef operon decreased virulence in mice more than 1,000-fold. Nonpolar mutations that disrupted sefA (encoding the major structural subunit) did not affect virulence, but mutations that disrupted sefD (encoding the putative adhesion subunit) resulted in a severe virulence defect. The results indicate that the putative SEF14 adhesion subunit is specifically required for a stage of the infection subsequent to transit across the intestinal barrier. Therefore, we tested whether SefD is required for uptake or survival in macrophages. The majority of wild-type bacteria were detected inside macrophages soon after i.p. infection, but the sefD mutants were not readily internalized by peritoneal macrophages. These results indicate that the potential SEF14 adhesion subunit is essential for efficient uptake or survival of S. enteritidis in macrophages. This report describes a role of fimbriae in intracellular infection, and indicates that fimbriae may be required for systemic infections at stages beyond the initial colonization of host epithelial surfaces.