ISSN:0267-1379    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The important contribution ofCampylobacterinfections to human enteric disease is well established. Recent completion of the genomic sequence of aCampylobacter jejunistrain has heralded a renaissance in the field ofCampylobacterpathogenesis research. With the application of novel, powerful technologies, our understanding of how these organisms mediate disease is set to evolve rapidly from its current, relatively neglected status.

ISSN:0267-1379    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The last year has seen new approaches to the diagnosis, treatment, and prevention of protozoal infections of the gastrointestinal tract. Some of the news is not good: new foodborne and swimming pool outbreaks of cyclosporiasis and cryptosporidiosis, respectively, occurred in North America; paromomycin was shown to be ineffective treatment for cryptosporidiosis; and these parasitic diseases continued to have a worldwide impact on human health. On the bright side, there were important advances in the understanding of the pathogenesis of cryptosporidiosis and the diagnosis of amebiasis and giardiasis, and some new leads on the treatment of cryptosporidiosis and refractory giardiasis. Finally, evidence was found of acquired mucosal immunity to amebiasis in Bangladeshi children, offering a guide for the development of an amebiasis vaccine. This review is not intended to be comprehensive, but contains a variety of articles that the authors hope will be of interest to the reader.

ISSN:0267-1379    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Helicobacter pyloriis known to be the cause of most gastric diseases, including both peptic ulcer disease and gastric cancer. In the absence of eradication, infection tends to be lifelong and the immune response ineffective in clearing the bacteria. A number of groups have investigated whether the immune clearance of infection can be achieved through a vaccination strategy, but to date, the results have been inconclusive. In fact, in most cases of natural infection, the host immune response leads to a chronic inflammation within the gastric mucosa that actually promotes the development of atrophy and neoplasia. In most cases, eradication of the organism leads to resolution of inflammation, which in many instances can result in reduction in atrophy and gastric cancer risk. This finding suggests that even at late stages, cancer progression is dependent, to a large extent, on infection/immune response. Work from a number of laboratories has led to the hypothesis that T-cells and the Th1 immune response, governed largely by host genetic factors, are strongly associated with theH. pylori-mediated induction of atrophy and cancer. Interleukin-1&bgr; appears to be a particularly important cytokine that inhibits acid secretion and increases serum gastrin levels, factors strongly associated with cancer induction. The induction byH. pyloriof cytokines and chemokines and growth-related genes is mediated by the MAPK and NF-&kgr;B signaling pathway. Recent studies have shown that NF-&kgr;B is activated through a NF-&kgr;B–inducing kinase/p21-activated kinase 1 pathway.H. pylorican also promote cellular apoptosis through a number of mechanisms, the most important of which is upregulation of the Fas/FasL pathway. Finally, understanding ofH. pyloripathogenesis has been broadened and deepened by the application of genomics and proteomics to the organism.

ISSN:0267-1379    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Current standard treatment regimens forHelicobacter pyloriinfection provide eradication rates 80 to 90%. These rates have been achieved with a variety of 1-week triple therapies using two antibiotics and an acid suppressant. Antibiotic resistance, which may develop during failed treatment, is becoming increasingly common and has led to studies of new regimens for primary therapy, and new strategies for salvage of failed therapy. Other regimens have been designed and tested with the aim of decreasing the cost of initial therapy or to improve compliance, but abbreviated regimens have high incidence of failure and may add to the problem of resistance. Increasing attention has been paid to the need for, and timing of, the determination of antibiotic resistance ofH. pyloriisolates either at the time of initial diagnosis or after treatment failure. New, simpler, and noninvasive methods are offered for follow-up to determine if eradication has been successful. Treatment regimens should be chosen based on local drug susceptibility patterns and the availability of approved therapeutic agents in each country.Established indications for testing forH. pyloriand administering therapy include active or inactive peptic ulcer disease, mucosa-associated lymphoid tissue (MALT) lymphoma, as well as hyperplastic polyps, hyperplastic gastropathy, postendoscopic resection for gastric malignancy, and acuteH. pylorigastritis. It is now largely accepted that noninvestigated dyspepsia is an indication for testing for and treatingH. pylori, but that dyspeptic symptoms shown not to be associated with ulcer (nonulcer dyspepsia) do not now provide an indication for testing. Controversial or unresolved indications for testing and treating include planned use of chronic antisecretory therapy, planned use of nonsteroidal anti-inflammatory drugs, and use as a general approach to the prevention of gastric cancer.

ISSN:0267-1379    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Immunocompromised patients, including patients with AIDS, solid organ and bone marrow transplant recipients, patients with leukemia and lymphoma, patients with inherited immune deficiencies, and patients on immunosuppressive therapy for a variety of disorders, are at risk for infections—particularly opportunistic infections, which, by definition, do not infect the healthy host. All systems of the body, including the gastrointestinal tract, are susceptible. The esophagus, stomach, small intestine, and large intestine are sites of infection for viruses, bacteria, fungi, and protozoa. Symptoms can range in severity from fevers of unknown etiology to life-threatening hemorrhage and perforation. This review summarizes recent case reports, clinical studies, and reviews pertaining to pathogens that uniquely cause disease, more frequently cause disease, or cause more severe disease in the immunocompromised host than in the immunocompetent host.

ISSN:0267-1379    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Despite the relative success of analogous approaches in soil, aquatic, and animal environments, the enhancement of human health through probiotic consumption has not been generally endorsed in modern medicine. Laboratory-based studies are elucidating the mechanisms that mediate the properties attributed to beneficial lactic acid bacteria andSaccharomycesspeciesin vivo.This research is now providing fundamental evidence to support observations of adhesion of probiotic species to intestinal tissue, antimicrobial activities, and immunomodulation. Probiotics appear to have a promising future in the treatment of certain disorders. Rigorously performed, controlled, double-blinded trials will overcome doubts relating to efficacyin vivoand open avenues along which probiotic-based therapies will rapidly progress. As a result of our emerging understanding of microbial activities and gene expressionin situ, novel strategies will combine complementary probiotic functionalities in the form of microbial consortia or genetically enhanced organisms. As scientific knowledge and biotechnologic proficiency advance at an accelerating pace, the requirement for informed legislation and for mechanisms of effectively delivering these therapies to the sites of their intended function may limit the applications of probiotics.

ISSN:0267-1379    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Risk factors for waterborne enteric infections are deduced primarily from outbreak surveillance data; however, in the United States, only a fraction of the estimated water-related outbreaks are reported through passive surveillance. In the past several years, advances in molecular detection techniques have furthered our knowledge about foodborne and waterborne causes of gastroenteritis, allowing the association of certain pathogens with biologic and exposure-related susceptibilities in their hosts. This article summarizes some of the recent data characterizing susceptibility to three common waterborne pathogens:Cryptosporidium, a protozoan; Norwalk-like virus; and the bacteriumEscherichia coliO157:H7. The infectious dose ofCryptosporidiumvaries by several orders of magnitude by strain, and repeated low-level exposure in drinking water may be protective. Some people may be innately immune to Norwalk-like virus, despite multiple exposures. A major risk factor forE. coliO157:H7 infection is exposure to shallow groundwater sources contaminated with animal waste.

ISSN:0267-1379    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0267-1379    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Molecular genetic analysis of colon cancers has established that the Wnt signaling pathway is involved in early tumor development. Mutation of midstream components can activate the pathway, making it independent of Wnt ligands and maintaining constant pressure to change target gene expression. The transcription factors that connect the pathway to target genes are members of the lymphoid enhancer factor/T-cell factor (LEF/TCF) family. The genes for two members of this family,TCF 7andLEF 1, produce full-length forms that mediate Wnt signals and truncated dominant negative forms that limit Wnt signals and may function as growth suppressors. Results from studies of their expression in colon cancer suggests that because Wnt-linked cancers progress to malignancy, there may be a strengthening of the Wnt signal by selective expression of the activating forms of LEF/TCFs and a bias against suppressing, truncated forms.

ISSN:0267-1379    

出版商:OVID    

年代:2002

数据来源: OVID