16SrRNA基因在快速诊断新生儿败血症的病原菌研究

目的探讨血液16SrRNA基因检测在新生儿败血症诊断中的应用价值。方法分析细菌16SrRNA基因保守区,设计一对通用引物扩增已知实验菌株,检测其特异性,用倍比稀释法检测其敏感性,同时进行血培养。结果已知实验菌株均获得920bp扩增产物,对照组中的人类基因组DNA、HBV—DNA和白色假丝酵母菌无相应产物。敏感性测试能达到lpg大肠杆菌DNA。PCR阳性率为31．7％（20／63）,血培养阳性率为14．3％（9／63）,两者比较有显著性差异（P〈0.05）。结论PCR检测血液细菌16SrRNA基因,具有特异性强,敏感度高等特点,能在临床推广应用。     

五株隐孢子虫18S rRNA部分基因克隆和序列分析

设计Nested PCR引物扩增牛源微小隐孢子虫Cryptospordium parvum、羊源微小隐孢子虫C. parvum、牛源安氏隐孢子虫C. andersoni、鸡源贝氏隐孢子虫C. baileyi及猪源隐孢子虫C. suis 18S rRNA基因突变区,PCR产物经克隆测序,其片段大小分别为212、213、213、213和210 bp.将测得的序列用DNAStar软件分析并与NCBI数据库中相同与相近种株序列进行相似性比较, 进行相似性分析并用TREECON软件绘制系统发育进化树.结果表明测得的5株隐孢子虫与各自相同种相似性为98.1%～100%,与其他种相似性为90.1%～98.6%.分析显示在此突变区设置特异酶切位点能区分开C. parvum, C. andersoni, C. baileyi与C. suis,位点分别是TaqI、BstUI、MseI.本研究为我国隐孢子虫分类、分子流行病学研究提供了新的方法.     

表达鼠精子Cyritestin蛋白的减毒沙门氏菌疫苗株的构建及其鉴定

目的 构建表达鼠精子eyritestin蛋白的可口服减毒沙让氏菌活疫苗株。方法 应用质粒TAZ83／13，将之进行双酶切获得含有成熟cyritestin蛋白cDNA序列的酶切片段。将其插入表达载体yA3149中，构建重组质粒pCFL。将该重组质粒转入鼠沙门氏伤寒杆菌疫苗株X4632和X4550中，以获得重组菌株X4632（pCFL)和X4550（pCFL)。结果 该两种无抗药性的重组菌株在体外营养选择压力下，可较稳定地携带重组质粒传代繁殖。X4550(pCFL)在体内可较稳定地害居于Peyer‘s结，肠系膜淋巴结和脾脏；X4632（pCFL)可较稳定地定居于Peyer‘s结。二者均可表达被抗cyritestin单抗（mAb)识别的重组cyritestin蛋白。口服该疫苗菌株无明显的毒性作用。结论 X4632（pCFL),X4550（pCFL)疫苗株的构建，为研究以cyritestin为靶抗原的精子抗原避孕疫苗打下了基础。     

吉林地区山羊中泰勒虫感染检测及其序列分析

泰勒虫病是由泰勒科(Theileriidae)泰勒属Theileria原虫引起经蜱传播的一种疾病,可以侵袭羊的网状内皮系统细胞和红细胞,本次研究的目的是了解我国吉林地区山羊中泰勒虫的感染情况以及主要的基因型.在吉林珲春地区采集70份山羊血液标本.基于泰勒虫18S rRNA基因,分两段设计扩增全长的属特异引物,对采集到的血液样本进行PCR检测,将扩增产物进行测序,与GenBank中注册的核苷酸序列进行同源性比较,采用MEGA5.0软件进行遗传发育分析.结果表明在吉林珲春地区采集到的山羊血液标本中有51只(72.9％)山羊感染了泰勒虫,通过测序获得近全长1 600 bp的泰勒虫基因序列(KC429038).经过Blast序列比对分析,与吕氏泰勒虫Theileria luwenshuni最接近,和T.luwenshuni(JX469518)相差一个碱基,同源性为99％.从构建的系统发育树可以看出本研究所获得序列与吕氏泰勒虫T.luwenshuni最接近位于同一小分支.本研究说明我国吉林地区山羊中泰勒虫感染较为普遍,初步认为吕氏泰勒虫可能为本地区的一个较为流行的基因型.     

16种常见凝固酶阴性葡萄球菌的快速分子鉴定

目的 建立对16种常见凝固酶阴性葡萄球菌(CNS)的快速分子鉴定.方法 用gap基因对16种常见CNS进行扩增和测序,获得序列在GenBank进行比对,构建进化树进行同源分析,同时与16S rRNA基因比较.结果 16种常见CNS中,gap基因相似率介于39% ～ 98%,人葡萄球菌和与人葡萄球菌亚种相似率最高(98%),腐生葡萄球菌与木糖葡萄球菌相似率最低(39％),16SrRNA基因相似率介于96% ～ 99%,至少2种细菌99%以上相似率,最多4种葡萄球菌99%以上相似率;进化树同源分析显示,两种方法在检测缓慢葡萄球菌与松鼠葡萄球菌、产色葡萄球菌与中间葡萄球菌和人葡萄球菌与人葡萄球菌亚种时,都有很高的可信度(99%以上),而对于其他10种细菌,gap基因同源分析有较少的不可靠信度(49%,56%),16S rRNA基因同源分析有较多不可靠信度(43%、43%、50%、56%、63%、65%、76%).结论 gap基因序列分析能够对16种常见CNS进行准确鉴定,同源分析可信度要明显优于16S rRNA基因.     

椰毒假单胞菌部分16SrRNA序列测定及其系统发育地位

采用聚合酶链反应（ＰＣＲ）扩增了椰毒假单胞菌代表菌株Ｔ７７０７的部分１６ＳｒＲＮＡ基因片段，将扩增片段克隆到Ｍ１３ｍｐ１９噬菌体，扩增后提取其单链ＤＮＡ，用ＤＮＡ测序仪进行测序。所得结果与已发表的其它已知假单胞菌的相应序列进行比较，计算出各菌之间的差异，并据此进行聚类。结果表明椰毒假单胞菌在系统发育上与Ｂｕｒｋｈｏｌｄｅｒｉａ属的成员关系密切，而与其它假单胞菌种的关系很远。这表明，椰毒假单胞菌应为Ｂｕｒｋｈｏｌｄｅｒｉａ属的一个种。     

一种新的沙门氏菌成簇重复序列的预测方法

目的建立一个新的、直观的鉴定和显示细菌基因组成簇重复序列的方法,了解沙门氏菌基因组成簇重复序列的组成特征。方法直接将细菌的基因组用滑动窗口法切割成重叠片段,每一个片段自体比对,利用Pip Maker生成共线性图。通过共线性图特征识别成簇重复序列区。结果用所设计方案-成簇重复序列预测器(CRpred)对鼠伤寒沙门氏菌LT2菌株基因组进行扫描,总共鉴定出151个成簇重复区。特征分析表明,这些成簇重复区包含低拷贝简单串联重复、高拷贝简单串联重复、间隔串联重复、反向回文重复和反向间隔重复等5种类型。此外,沙门氏菌基因组中有9个复杂重复区域无法使用上述模式进行归类。结论提出了一个新的、简便直观的基因组成簇重复序列的鉴定方法,为搜寻成簇的、规律间隔的短回文重复序列(CRISPR)、数目可变串联重复序列(VNTR)以及其他重复序列相关研究提供支持。     

一株副猪链球菌的鉴定及生物学特征分析

目的对从一患者脑脊液中分离的副猪链球菌菌株进行病原学鉴定, 并了解其生物学特征。方法对该菌株使用分离培养、生化鉴定、16S rRNA和管家基因recN基因分析、平均核苷酸一致性分析(ANI)、药敏实验、耐药基因、毒力基因分析等方法进行分析。结果该菌为革兰阳性球菌、在血平板上草绿色溶血, 经16S rRNA、recN基因及全基因组序列分析为副猪链球菌, 对多种抗生素敏感, 并携带有黏附类等多种毒力基因。结论副猪链球菌可导致人类感染, 可通过基因测序方法进行诊断。     

反相高效液相色谱法和16S rRNA序列分析法对分枝杆菌分型鉴别的比较研究

目的比较反相高效液相色谱法(RP-HPLC)和16S rRNA序列分析法对分枝杆菌分型鉴别的异同。方法将《伯杰细菌鉴定手册》中载入的49种分枝杆菌模式株接种于改良罗氏培养基上,置于最适温度下孵育。挑取生长良好且无污染的培养物,一部分经皂化和酸化提取分枝菌酸并衍生后,采用反相高效液相色谱法进行分枝菌酸指纹图谱构建;另一部分经裂解和PCR扩增,获得DNA,纯化后,采用核酸分析仪进行16S rRNA序列测定。结果 49种分枝杆菌模式株中,采用RP-HPLC分析时,单簇峰的结核分枝杆菌、牛分枝杆菌和胃分枝杆菌,双簇峰的爱知分枝杆菌和罗德岛分枝杆菌,三簇峰的南非分枝杆菌和母牛分枝杆菌共7种因各组内相对保留时间和相对峰高比值相近而难以进行鉴别;采用16S rRNA序列分析法分析时,产鼻疽分枝杆菌和塞内加尔分枝杆菌、溃疡分枝杆菌和海分枝杆菌、堪萨斯分枝杆菌和胃分枝杆菌、龟亚分枝杆菌和龟脓分枝杆菌以及结核分枝杆菌复合群(结核分枝杆菌、牛分枝杆菌、田鼠分枝杆菌和非洲分枝杆菌)共12种因各组内基因序列相似性百分比为100%而难以进行鉴别。通过两种分型鉴别方法的比较,可见除结核分枝杆菌和牛分枝杆菌外,两种分型方法相互补充,可将49种分枝杆菌模式株中的47种进行明确鉴别。结论分枝菌酸RP-HPLC和16S rRNA序列分析法均为分枝杆菌的分型鉴定提供了准确和有效的技术方法。两种方法相互借鉴能准确地将大多数分枝杆菌鉴定到种。     

两株临床分离的金黄杆菌的鉴定和系统发育分析

目的对临床痰液和中段尿标本分离的SQ219和SQ220进行生物学特性、系统进化和临床意义分析。方法观察菌株的培养特性及生理生化特征;用VITEK2全自动微生物鉴定和药敏分析仪及MALDI-TOF质谱仪鉴定细菌;利用相关软件对细菌16S rRNA和核心基因组作系统发育分析及基因组平均核苷酸一致性(ANI)分析。结果 SQ219和SQ220为革兰阴性杆菌, 专性需氧, 触酶和氧化酶阳性, 无动力;在30℃、pH7和不含NaCl的培养基中生长最佳;SQ220可在血平板上产生黄色素但SQ219不产生;SQ219和SQ220对氨曲南、阿米卡星、妥布霉素、黏菌素耐药, 与金黄杆菌属药敏表型一致。SQ219和SQ220总长分别为5.08 Mb和4.80 Mb, G+C含量分别为36.72%和36.36%, 均预测到β-内酰胺类耐药基因(blaCGA)。16S rRNA系统发育分析表明SQ219、SQ220与啤酒神金黄杆菌DSM18014T相似性最高, 分别为98.93%和98.36%;核心基因组进化分析显示SQ219、SQ220与啤酒神金黄杆菌DSM18014T的进化关系最近。然而, 两株菌与啤酒神...     

Salmonella enterica serovar Typhi plasmid pRST98-mediated inhibition of autophagy promotes bacterial survival in infected fibroblasts

pR_ST98 is a chimeric plasmid isolated from Salmonella enterica serovar typhi (S. typhi) and mediates both drug-resistance and virulence of S. typhi. Autophagy has been recently reported as an important component of the innate immune response against intracellular pathogen. In this study, we investigated the effect of pR_ST98 on cellular autophagy, apoptosis and bacterial survival in infected fibroblasts. S. typhi strain ST₈ carrying pR_ST98, Salmonella typhimurium strain SR-11 carrying a 100 Kb virulent plasmid, and avirulent S. typhi strain ST₁₀ without plasmid were tested in this experiment. Results showed that embryonic fibroblasts infected with ST₈ containing pR_ST98 had decreased autophagy accompanied by increased bacterial survival and apoptosis. Further study showed that autophagy inducer rapamycin reversed pR_ST98-mediated inhibition of autophagy and reduced apoptosis in infected fibroblasts. Our data indicate that pR_ST98 can inhibit autophagy, thus facilitating S. typhi survival and promoting apoptosis of host cells. This study contributes to understanding the underlying mechanism of pR_ST98-mediated virulence in S. typhi.     

Fingerprinting of Salmonella enterica subsp. enterica serovar Enteritidis by ribotyping

Objective: To carry out an epidemiologic evaluation of Salmonella enterica subsp. enterica serovar Enteritidis outbreaks in households and small communities by means of rRNA gene restriction pattern analysis (ribotyping).
Method: One hundred Enteritidis isolates dating from 1989 to 1994 which could be allocated epidemiologically to different sources or to small community outbreaks were investigated with ribotyping, a fingerprinting method in which bacterial DNA is hybridized with the biotin-labeled plasmid pKK 3535 containing a ribosomal RNA operon of Escherichia coli to determine the ribosomal RNA gene restriction patterns.
Results: Four different ribotyping patterns were found with the restriction endonuclease Sma I and nine with Sph I. Ribotypes of isolates which could be allocated epidemiologically to a common source usually corresponded. Almost 60% of the Enteritidis infections had the ribotyping pattern Sph I-A. In contrast, this pattern was not found in any of the five Enteritidis strains isolated in 1989. The suspicion that Enteritidis phage type 4 infections are caused by consumption of insufficiently heated eggs is supported by the fact that the ribotyping pattern Sph 1-A was found in isolates from eggs and from human specimens.
Conclusions: As patterns Sph I-A and Sma I-J appeared in 58% and 75% of the isolates, respectively, ribotyping cannot be used for the differentiation between various outbreaks with these two patterns. In cases where the Enteritidis strains showed less frequent patterns, ribotyping seems to be a practical tool for the identification of infection chains. In addition newly appearing ribotyping patterns can give information about the epidemiologic development of Enteritidis infection.     

Contribution of the csgA and bcsA genes to Salmonella enterica serovar Pullorum biofilm formation and virulence

Salmonella biofilm formation is important to environmental stress resistance and virulence. However, the roles of the csgA and bcsA genes, which affect curli protein and cellulose production, respectively, in Salmonella enterica serovar Pullorum, are unknown. Here we constructed deletions in the csgA and bcsA genes in S. enterica serovar Pullorum strain S6702 and evaluated several aspects of biofilm formation and virulence. ΔcsgA showed decreased production of curli fimbriae, while ΔbcsA had reduced cellulose production. Both mutants had a reduced ability to form biofilms. ΔcsgA was reduced in adhesion and invasion to HeLa cells and exhibited decreased intracellular proliferation in HD11 macrophages. ΔbcsA exhibited increased proliferation in HD11 cells and replicated better in chicken spleens, as compared to the wild-type strain. ΔcsgA virulence was attenuated in assays involving oral challenge of one-day-old chickens.     

Molecular epidemiology of ampicillin-resistant clinical isolates of Salmonella enterica serovar Typhimurium

Thirty-nine multiresistant Salmonella enterica serovar Typhimurium (S. Typhimurium) isolates were obtained from 33 children and 6 adults hospitalized from 1996 to 1999 in the University Hospital of Amiens (France). S. Typhimurium was cultured from stools (n=36), blood samples (n=2) and peritoneal fluid (n=1). These isolates were characterized by biotyping, antibiotic susceptibility test, RAPD-PCR, and PFGE typing. Emergence of pentaresistant S. Typhimurium isolates (phenotype ACSSuTe) was observed, and five of them were resistant to nalidixic acid and of intermediate susceptibility to pefloxacin. Genotypic analysis of both RAPD and PFGE results showed that there were 7 different patterns. Thirty-three isolates gave an identical pattern (AI) and were considered as epidemic isolates; the six remaining patterns (each containing one isolate) corresponded to sporadic cases. Antibiotic susceptibility patterns, RAPD and PFGE patterns subdivided the 39 isolates into 9 clonally related groups. One of them (pattern AI and R-pattern a) was implicated in 74% of the cases.     

Construction and characterization of a cigR deletion mutant of Salmonella enterica serovar Pullorum

Salmonella enterica serovar Pullorum (S. Pullorum) is the causative agent of pullorum disease (PD) and results in severe economic losses to the poultry industry. As a Salmonella type III secretion system 2 (T3SS2) effector and predicted membrane protein, CigR is encoded by the cigR gene within Salmonella pathogenicity island 3 (SPI3). In order to research the influence of the cigR gene on S. Pullorum, a cigR mutant of S. Pullorum S06004 was constructed by the lambda Red recombination system, and then its characterization was analysed. Lack of cigR did not affect the growth and biochemical properties, but resulted in decreased biofilm formation. The mutant strain was stable with the deletion of the cigR gene. Macrophage infection assay and in vivo competition assay showed that the mutant strain increased the replication and/or survival ability in the HD11 cell line and in chickens compared to that of the parent strain, the median lethal dose (LD₅₀) of the mutant strain was one-fifth of the parent strain for 2-day-old chickens when injected intramuscularly. These results demonstrate CigR plays roles in biofilm formation and pathogenicity of S. Pullorum, deletion of cigR can significantly decrease biofilm formation and significantly increase virulence.     

Construction of pSPI12-cured Salmonella enterica serovar Pullorum and identification of IpaJ as an immune response modulator

In Salmonella, plasmids participate in many pathways involved in virulence, metabolism, and antibiotic resistance. To investigate the function of the ipaJ gene in a multi-copy plasmid pSPI12 prevalent in Salmonella enterica serovar Pullorum (S. Pullorum), we established a method to eliminate the plasmid and constructed the plasmid-cured bacteria C79-13-ΔpSPI12 by using the suicide vector pDM4. Briefly, a 500?bp fragment ipaJU from pSPI12 was cloned into pDM4 and transformed into S. Pullorum C79-13 by conjugative transfer. After homologous recombination, the suicide vector was inserted into pSPI12 to produce pSPI12-pDM4-ipaJU. Induction of the expression of the sacB gene in the suicide vector killed the bacteria harbouring plasmid, while the progeny losing the plasmid survived in the plate with sucrose. The plasmid-cured strain showed extremely decreased ability to infect chicken macrophage HD11 cells and LMH hepatic epithelial cells compared to wild type strain and complementary strain carrying ipaJ. Additionally, IFN-γ mRNA levels were up-regulated in HD11 cells or chicken spleens infected by plasmid-cured strain, but no difference was detected in IL-4 among the three strains. Transforming ipaJ into S. Enteritidis also decreased expression of proinflammatory cytokines in infected macrophages or chicken spleens compared to wild type strain. These results suggest that the ipaJ gene in pSPI12 is involved in S. Pullorum infection and that IpaJ protein modulates immune response.     

A rapid method to identify Salmonella enterica serovar Gallinarum biovar Pullorum using a specific target gene ipaJ

Salmonella enterica serovar Gallinarum biovar Pullorum (S. Pullorum) is the pathogen of pullorum disease, which leads to severe economic losses in many developing countries. Traditional methods to identify S. enterica have relied on biochemical reactions and serotyping, which are time-consuming with accurate identification if properly carried out. In this study, we developed a rapid polymerase chain reaction (PCR) method targeting the specific gene ipaJ to detect S. Pullorum. Among the 650 S. Pullorum strains isolated from 1962 to 2016 all over China, 644 strains were identified to harbour ipaJ gene in the plasmid pSPI12, accounting for a detection rate of 99.08%. Six strains were ipaJ negative because pSPI12 was not found in these strains according to whole genome sequencing results. There was no cross-reaction with other Salmonella serotypes, including Salmonella enterica serovar Gallinarum biovar Gallinarum (S. Gallinarum), which show a close genetic relationship with S. Pullorum. This shows that the PCR method could distinguish S. Gallinarum from S. Pullorum in one-step PCR without complicated biochemical identification. The limit of detection of this PCR method was as low as 90?fg/μl or 10² CFU, which shows a high sensitivity. Moreover, this method was applied to identify Salmonella isolated from the chicken farm and the results were consistent with what we obtained from biochemical reactions and serotyping. Together, all the results demonstrated that this one-step PCR method is simple and feasible to efficiently identify S. Pullorum.     

A Salmonella enterica serovar Typhi plasmid induces rapid and massive apoptosis in infected macrophages

pR_ST98 is a chimeric plasmid isolated from Salmonella enterica serovar Typhi (S. typhi) that mediates the functions of drug resistance and virulence. Previously, we reported that Salmonella plasmid virulence (spv) genes were present in S. typhi. In our current study, we investigated whether plasmid pR_ST98 exhibits significant cytotoxicity in macrophages. pR_ST98 was transferred into the avirulent Salmonella enterica serovar Typhimurium (S. typhimurium) strain RIA to create the transconjugant pR_ST98/RIA. The standard S. typhimurium virulent strain SR-11, which carries a 100-kb virulence plasmid, was used as a positive control. The bacterial strains were incubated with a murine macrophage-like cell line (J774A.1) in vitro. Apoptosis of J774A.1 cells was examined by electron microscopy and flow cytometry after annexin-V/propidium iodide labeling, and the survival of Salmonella strains in J774A.1 cells was determined. Results showed that macrophages infected with strain pR_ST98/RIA displayed greater levels of apoptosis than those infected with RIA and that pR_ST98 may increase bacterial survival in macrophages. Further studies showed that the pR_ST98-induced death of macrophages was associated with the loss of mitochondrial membrane potential and that pR_ST98 may activate caspase-9 and then caspase-3. The research data indicate that the virulence of bacteria that contain the pR_ST98 plasmid is enhanced; the presence of this plasmid increases the survival of the bacterial pathogen and acts through the mitochondrial pathway to mediate macrophage apoptosis.     

Phylogenetic analysis of Pasteurella multocida subspecies and molecular identification of feline P. multocida subsp. septica by 16S rRNA gene sequencing

Pasteurella multocida is commonly found in the oral cavity of cats and dogs. In humans it is known as an opportunistic pathogen after bites from these animals. Phenotypic identification of P. multocida based on biochemical reactions is often limited and usually only done on a species level, even though 3 subspecies are described. For molecular taxonomy and diagnostic purposes a phylogenetic analysis of the three subspecies of P. multocida based on their 16S rRNA (rrs) gene sequence was therefore carried out. We found P. multocida subsp. septica on a distinguished branch on the phylogenetic tree of Pasteurellaceae, due to a 1.5% divergence of its rrs gene compared to the two other, more closely related subspecies multocida and gallicida. This phylogenetic divergence can be used for the identification of P. multocida subsp. septica by rrs gene determination since they form a phylogenetically well isolated and defined group as shown with a set of feline isolates. Comparison to routine phenotypic identification shows the advantage of the sequence-based identification over conventional methods. It is therefore helpful for future unambiguous identification and molecular taxonomy of P. multocida as well as for epidemiological investigations.