Development of vaccine for enterohemorrhagic Escherichia coli infection

Efforts on the development of vaccines against enterohemorrhagic Escherichia coli (EHEC) infection has been described in this review. Two kinds of vaccines were developed and these have been targeted for in humans and cattle. One vaccine candidate is toxoid, which uses an inactive form of Shiga toxin(Stx). A part of B subunit, each B or A subunit or one or two amino acid mutated holotoxin were developed as a toxoid vaccine candidate. The other candidate was bacterial surface antigen such as a live attenuated EHEC and hybrid between non-toxic LPS and toxoid. A live attenuated vaccine against EHEC O26: H11, O157: H7, O139: H1 were developed. Further a live attenuated vaccine candidate of Vibrio cholerae O1 expressing Stx1-B, Shigella flexneri expressing S. dysenteriae O-antigen and Stx1-B, or Salmonella Typhimurium expressing O111 antigen were developed. Hybrid type vaccine candidates were also developed with O111 LPS and tetanus toxoid, O157 LPS and exotoxin, and O157 LPS and Stx1-B.     

Treatment and prevention of enterohemorrhagic Escherichia coli infection and hemolytic uremic syndrome

Over a quarter century after the discovery of verocytotoxin and the first report by Karmali and colleagues of cases of postdiarrheal hemolytic uremic syndrome (HUS) caused by verotoxigenic Escherichia coli (VTEC), otherwise known as Shiga-toxigenic E. coli (STEC), successful treatment of these infections has remained elusive. This is because the pathological insult producing the clinical picture of HUS occurs early in the disease process and curtails quickly, making treatment intervention a largely vain hope. Nevertheless, understanding of the pathogenesis of HUS has expanded and, as a result, we can expect a future breakthrough in the treatment of this life-threatening condition. This review examines the pathogenesis of HUS and explores targets for treatment, including the reasons why certain therapies have failed and why future therapies could be successful. This review also examines the status of vaccine development in prevention of VTEC/STEC disease.     

Treatment and prevention of enterohemorrhagic Escherichia coli infection and hemolytic uremic syndrome

Over a quarter century after the discovery of verocytotoxin and the first report by Karmali and colleagues of cases of postdiarrheal hemolytic uremic syndrome (HUS) caused by verotoxigenic Escherichia coli (VTEC), otherwise known as Shiga-toxigenic E. coli (STEC), successful treatment of these infections has remained elusive. This is because the pathological insult producing the clinical picture of HUS occurs early in the disease process and curtails quickly, making treatment intervention a largely vain hope. Nevertheless, understanding of the pathogenesis of HUS has expanded and, as a result, we can expect a future breakthrough in the treatment of this life-threatening condition. This review examines the pathogenesis of HUS and explores targets for treatment, including the reasons why certain therapies have failed and why future therapies could be successful. This review also examines the status of vaccine development in prevention of VTEC/STEC disease.     

Genetic diversity of enterohemorrhagic Escherichia coli

Enterohemorrhagic Escherichia coli(EHEC) causes diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. Genomic comparison of an EHEC O157: H7 strain isolated from the Sakai outbreak and a benign laboratory strain K-12 revealed that acquisition of a large amount of foreign DNA has promoted the genetic diversification of E. coli strains. In the emergence of O157: H7, bacteriophages, in particular, played an important role. EHEC are a group of strains with several serotypes, each belonging to different E. coli lineages. Even in an O157 lineage, significant phenotypic and genetic heterogeneities are observed. Recent knowledge on the significance and the generating mechanism of such heterogeneity in EHEC strains are summarized.     

Emerging foodborne pathogens: enterohemorrhagic Escherichia coli.

In 1982, a new pathogen caused an outbreak of hemorrhagic colitis in this country. This new pathogen, Escherichia coli O157:H7, was not a known enteropathogen prior to this time. Since 1982, this organism has become the most commonly isolated pathogen from patients with bloody stools. Health officials estimate that E. coli O157:H7 causes 20,000 cases of hemorrhagic colitis annually in the U.S. Approximately 5% of all hemorrhagic colitis patients experience serious sequelae involving hemolytic anemia, thrombocytopenia, and kidney failure, and about 250 patients die each year with E. coli O157:H7 hemorrhagic colitis and sequelae. Even as many clinical laboratories become more efficient at detecting E. coli O157:H7 using simple media, other strains of enterohemorrhagic E. coli are appearing as causes of hemorrhagic colitis and hemolytic uremic syndrome. These non-O157:H7 are more difficult to detect and identify, and present a challenge to clinical microbiologists.     

Prevention and treatment of enterohemorrhagic Escherichia coli infections in humans

Infections with enterohemorrhagic Escherichia coli (EHEC) result in various clinical symptoms and outcomes ranging from watery or bloody diarrhea to the life-threatening hemolytic-uremic syndrome (HUS). Shiga toxins (Stxs) are supposed to play a major role in the pathogenesis of EHEC infections; however, the role of other putative virulence factors is not fully elucidated. So far, there is only supportive therapy available for the treatment of both EHEC-associated diarrhea and HUS. Antibiotic therapy for the treatment of EHEC-associated diarrhea is discussed. In recent years other therapeutic strategies have been developed, including Gb3 receptor analogues, that bind Stx in the gut or in the circulation, passive immunization with Stx-neutralizing monoclonal antibodies, or active immunization with Stx1 And Stx2 toxoids as a preventive procedure. These approaches have been demonstrated to be effective in animal models but clinical trials are lacking.     

黑龙江省肠出血性大肠埃希菌遗传基因型别的研究

目的 对肠出血性大肠埃希菌(EHEC)的遗传基因刑别进行不同分子分型方法的对比研究,从分子流行病学角度分析黑龙江省EHEC的检出情况,并对多位点串联重复序列分析(MLVA)分型方法用于 EHEC 的分型效果进行评价.方法 采用毒力基因鉴定、核酸脉冲场凝胶电泳(PFGE)与MLVA 3种方法对70株EHEC进行遗传基因型...     

β-半乳糖苷酶基因在早期诊断急性胰腺炎继发肠源性感染中的应用

目的　肠道细菌移位是导致急性胰腺炎 (AP)检测患者继发细菌感染的重要原因 ,本研究采用聚合酶链反应 (PCR)检测患者血中大肠杆菌特异性 β半乳糖苷酶基因旨在早期诊断AP并发肠源性感染。方法　 14例AP患者采用APAPACHEⅡ疾病严重程度评分及BalthazarCT分级评分系统对患者入院时的病情及影像学进行评分。APACHEⅡ≥ 8分或胰腺BalthazerCT分级达到D级或伴有坏死被认为是重症急笥胰腺炎 (SAP)。所有患者于入院后第 7天抽血行血培养、血浆内毒素水平测定及提取全血DNA作PCR。结果　 14例AP患者中 4例为SAP ,余 10例为轻型急性胰腺炎 (MAP)。所有患者入院第 7天血培养均为阴性 ,但 4例SAP及 1例MAP患者血PCR显示阳性结果 ,总阳性率为 36 % ,其中SAP 4例患者全部阴性 ,而MAP患者阳性率仅为 1 10。PCR阳性者APACHEⅡ评分平均 8 4± 1 4,显著高于阴性者 (1 7± 1 3分 ) ,P <0 0 5 ;PCR阳性者血浆内毒素水平亦明显高于阴性者 (0 32 3± 0 0 6 3EU/mlvs 0 136± 0 0 42EU/ml,P <0 0 5 )。结论　大肠杆菌 β半乳糖苷酶基因可作为诊断急性胰腺炎继发肠源性感染的标志物     

肠出血性大肠埃希菌酸抗性机制的研究进展

酸抗性是肠出血性大肠埃希菌重要的毒力因子之一。抗酸反应被认为是影响细菌生存及致病性的重要因素。随着分子生物学的发展,对肠出血性大肠埃希菌抗酸反应机制的研究越来越深入。本文就近年来有关肠出血性大肠埃希菌与σs因子相关的抗酸反应机制的研究做一综述。     

Multiplex PCR for detection of trait and virulence factors in enterohemorrhagic Escherichia coli serotypes

A multiplex PCR assay was developed which allowed the simultaneous detection of five trait genes or virulence markers in enterohemorrhagic Escherichia coli (EHEC) serotypes. A primer pair, designed to detect a single base-pair mutation in the uidA gene, is specific only for the prototypic EHEC of O157:H7 serotype and its toxigenic, non-motile variants. In a similar way, primers to the eaeA gene of the gamma-intimin derivative specifically detects strains in the EHEC 1 clonal group, which consists mostly of O157:H7 and some O55:H7 serotypes. The other three primer pairs, specific for stx1, stx2 and both variants of ehxA genes, will detect the presence of these virulence genes in all EHEC serotypes. Analysis of 34 strains, including various serotypes of EHEC, Shiga toxin-producing E. coli and enteropathogenic E. coli, confirmed that the multiplex PCR assay detected the presence of these genes in a manner consistent with the known genotype of each respective strains.     

The clinical significance of colonoscopy in hemorrhagic colitis due to enterohemorrhagic Escherichia coli O157:H7 infection

BACKGROUND AND STUDY AIMS: Although hemorrhagic colitis due to enterohemorrhagic Escherichia coli O157:H7 (O157) infection has recently attracted increasing attention as an important enteric infection, the colonoscopic findings associated with this disease have not been sufficiently characterized. The aim of this study is to characterize the colonoscopic features of hemorrhagic colitis due to O157 infection. PATIENTS AND METHODS: The colonoscopic findings in ten patients with hemorrhagic colitis due to O157 infection were retrospectively reviewed. To assess the severity of inflammation in each part of the large intestine, colonoscopic findings were categorized into four grades: grade 1, intact mucosa; grade 2, sporadic erythema and erosion; grade 3, mostly diffuse inflammation; and grade 4, diffuse, severe inflammation. RESULTS: Eight out of ten patients had grade 4 findings in the cecum and ascending colon, grade 3 in the transverse colon and descending colon, and grade 2 in the sigmoid colon. Two of these eight patients also had grade 4 inflammation in the proximal transverse colon. Five of these eight patients revealed longitudinal ulcer-like lesions in the transverse colon and/or descending colon. The remaining two patients had grade 3 findings in the cecum to the descending colon and grade 2 findings in the sigmoid colon. All patients exhibited grade 1 finding in the terminal ileum and the rectum. Based on these colonoscopic findings, the ten patients were divided into the typical group (eight patients) and the mild-type group (two patients). CONCLUSIONS: The characteristic colonoscopic findings in most patients with hemorrhagic colitis due to O157 infection were as follows: 1) severe inflammation, including primarily marked edema and facile hemorrhage, and 2) inflammation predominating at the right-side colon; and 3) frequent appearance of longitudinal ulcer-like lesions.     

多重PCR检测肠出血性大肠埃希菌O157：H7

目的 建立一种快速、特异的检测肠出血性大肠埃希菌O157:H7菌株的多重PCR方法。 方法 针对O157:H7菌株的O157、H7抗原特异基因rfbE O157、fliC H7以及stx1、stx2、eaeA和hlyA四种毒力基因设计相应引物,在同一扩增体系中进行PCR反应,通过优化多重PCR 反应条件和循环参数,建立检测O157:H7菌株的多重PCR方法,并测定其特异性和灵敏度。 结果 6 对特异性引物各自扩增相应的基因片段,检测结果与常规PCR 获得的结果一致。细菌纯培养物的检测灵敏度为1.33×10⁴ CFU。 结论 该多重PCR方法能在一次检测中同时反映待测菌株是否为肠出血性大肠埃希菌O157:H7及其携带毒力基因的情况,可为O157:H7大肠埃希菌感染的诊断及流行病学调查提供一种简便、快速的检测手段。     

Pathogenesis of enterohaemorrhagic Escherichia coli infection

EHEC is an emergent pathogen which causes haemorrhagic colitis and complications of the potentially fatal HUS. The main virulence factors are the phage-encoded Shiga toxin and the intimate attachment to host cells. Shiga toxin affects cells not only by inhibiting protein biosynthesis but also through the induction of signalling cascades leading to apoptosis. The locus of enterocyte effacement (LEE) encodes a type III secretion system that translocates bacterial effector proteins into the host cell cytoplasm. Intimate attachment is mediated through interactions of the bacterial outer-membrane protein Intimin and the translocated intimin receptor (Tir) on the host cells. Recently, a very rare serogroup strain in humans of E. coli 0104, which carries a stx2a gene in a typical type of EAggEC, appeared in EU and caused a big outbreak of haemorrhagic colitis and HUS.     

Escherichia coli O157 infection mimicking acute appendicitis: usefulness of computed tomography for differential diagnosis

A 19-year-old man was admitted to our hospital with acute abdominal pain in the right lower quadrant. He had had mild diarrhea, of 1 days duration, 2 days before admission. Although physical findings were consistent with a diagnosis of acute appendicitis, computed tomography findings showed marked wall thickening from the ascending colon to the cecum, findings which were similar to those in patients with hemorrhagic colitis due to Escherichia coli O157. Instead of emergency laparotomy, the patient was treated with antimicrobial agents, which led to rapid recovery. Diagnosis of intestinal infection due to E. coli O157 was established later, as serum antibody against lipopolysaccharide of E. coli O157 was positive. E. coli O157 infection should be included in the differential diagnosis of diseases that exhibit marked wall thickening of the right colon on CT in patients with acute abdominal pain in the right lower quadrant who have mild transient diarrhea.     

Comparative analysis of methods for laboratory diagnosis of Lyme's disease in early stages of infection

Different methods of laboratory diagnostics were comparatively analyzed in examining 25 patients at the early infection stage. Sera were measured by using various serological reactions. Specific antibodies were determined by using the reaction of indirect immune-fluorescence (RIIF), the immune-enzyme analysis (IEA) and the complement-binding reaction (CBR) in 83.1%, 54.4% and 12.5% of cases, respectively. Essential differences in sensitivity were detected between the above methods. RIIF was proven to be a reliable and sufficiently sensitive method in the laboratory diagnostics of Lyma's disease. While the use of two methods, i.e. RIIF and IEA, ensures the highest percentage of detection of antibodies to the causative agent of Lyma's disease.