The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Myron M Levine - One of the best experts on this subject based on the ideXlab platform.
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effect of wild type Shigella species and attenuated Shigella vaccine candidates on small intestinal barrier function antigen trafficking and cytokine release
PLOS ONE, 2014Co-Authors: Maria Fiorentino, Marcelo B Sztein, Myron M Levine, Alessio FasanoAbstract:Bacterial dysentery due to Shigella species is a major cause of morbidity and mortality worldwide. The pathogenesis of Shigella is based on the bacteria's ability to invade and replicate within the colonic epithelium, resulting in severe intestinal inflammatory response and epithelial destruction. Although the mechanisms of pathogenesis of Shigella in the colon have been extensively studied, little is known on the effect of wild-type Shigella on the small intestine and the role of the host response in the development of the disease. Moreover, to the best of our knowledge no studies have described the effects of apically administered Shigella flexneri 2a and S. dysenteriae 1 vaccine strains on human small intestinal enterocytes. The aim of this study was to assess the coordinated functional and immunological human epithelial responses evoked by strains of Shigella and candidate vaccines on small intestinal enterocytes. To model the interactions of Shigella with the intestinal mucosa, we apically exposed monolayers of human intestinal Caco2 cells to increasing bacterial inocula. We monitored changes in paracellular permeability, examined the organization of tight-junctions and the pro-inflammatory response of epithelial cells. Shigella infection of Caco2 monolayers caused severe mucosal damage, apparent as a drastic increase in paracellular permeability and disruption of tight junctions at the cell-cell boundary. Secretion of pro-inflammatory IL-8 was independent of epithelial barrier dysfunction. Shigella vaccine strains elicited a pro-inflammatory response without affecting the intestinal barrier integrity. Our data show that wild-type Shigella infection causes a severe alteration of the barrier function of a small intestinal cell monolayer (a proxy for mucosa) and might contribute (along with enterotoxins) to the induction of watery diarrhea. Diarrhea may be a mechanism by which the host attempts to eliminate harmful bacteria and transport them from the small to the large intestine where they invade colonocytes inducing a strong inflammatory response.
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Prevalence of Shigella Enterotoxin 1 among Shigella Clinical Isolates of Diverse Serotypes
The Journal of infectious diseases, 1995Co-Authors: Fernando R. Noriega, Alessio Fasano, Fang Ming Liao, Samuel B. Formal, Myron M LevineAbstract:Shigella enterotoxin 1 (ShET1) is a novel, iron-dependent, toxin encoded by chromosomal genes (set1). To determine the prevalence of this enterotoxin, 172 Shigella clinical isolates (and 10 enteroinvasive Escherichia coli [EIEC]) from distant areas worldwide, representing all 4 groups and 45 serotypes of Shigella, were screened for set1 by DNA colony hybridization and polymerase chain reaction amplification. set1 was present in all 22 Shigella flexneri 2a strains tested but was rare in isolates of other Shigella serotypes (3.3%, 5/150) and not found in EIEC (0/10). That ShET1 is found almost exclusively in S. flexneri 2a may help explain the epidemiologic predominance of this serotype in the developing world.
Alessio Fasano - One of the best experts on this subject based on the ideXlab platform.
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effect of wild type Shigella species and attenuated Shigella vaccine candidates on small intestinal barrier function antigen trafficking and cytokine release
PLOS ONE, 2014Co-Authors: Maria Fiorentino, Marcelo B Sztein, Myron M Levine, Alessio FasanoAbstract:Bacterial dysentery due to Shigella species is a major cause of morbidity and mortality worldwide. The pathogenesis of Shigella is based on the bacteria's ability to invade and replicate within the colonic epithelium, resulting in severe intestinal inflammatory response and epithelial destruction. Although the mechanisms of pathogenesis of Shigella in the colon have been extensively studied, little is known on the effect of wild-type Shigella on the small intestine and the role of the host response in the development of the disease. Moreover, to the best of our knowledge no studies have described the effects of apically administered Shigella flexneri 2a and S. dysenteriae 1 vaccine strains on human small intestinal enterocytes. The aim of this study was to assess the coordinated functional and immunological human epithelial responses evoked by strains of Shigella and candidate vaccines on small intestinal enterocytes. To model the interactions of Shigella with the intestinal mucosa, we apically exposed monolayers of human intestinal Caco2 cells to increasing bacterial inocula. We monitored changes in paracellular permeability, examined the organization of tight-junctions and the pro-inflammatory response of epithelial cells. Shigella infection of Caco2 monolayers caused severe mucosal damage, apparent as a drastic increase in paracellular permeability and disruption of tight junctions at the cell-cell boundary. Secretion of pro-inflammatory IL-8 was independent of epithelial barrier dysfunction. Shigella vaccine strains elicited a pro-inflammatory response without affecting the intestinal barrier integrity. Our data show that wild-type Shigella infection causes a severe alteration of the barrier function of a small intestinal cell monolayer (a proxy for mucosa) and might contribute (along with enterotoxins) to the induction of watery diarrhea. Diarrhea may be a mechanism by which the host attempts to eliminate harmful bacteria and transport them from the small to the large intestine where they invade colonocytes inducing a strong inflammatory response.
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Prevalence of Shigella Enterotoxin 1 among Shigella Clinical Isolates of Diverse Serotypes
The Journal of infectious diseases, 1995Co-Authors: Fernando R. Noriega, Alessio Fasano, Fang Ming Liao, Samuel B. Formal, Myron M LevineAbstract:Shigella enterotoxin 1 (ShET1) is a novel, iron-dependent, toxin encoded by chromosomal genes (set1). To determine the prevalence of this enterotoxin, 172 Shigella clinical isolates (and 10 enteroinvasive Escherichia coli [EIEC]) from distant areas worldwide, representing all 4 groups and 45 serotypes of Shigella, were screened for set1 by DNA colony hybridization and polymerase chain reaction amplification. set1 was present in all 22 Shigella flexneri 2a strains tested but was rare in isolates of other Shigella serotypes (3.3%, 5/150) and not found in EIEC (0/10). That ShET1 is found almost exclusively in S. flexneri 2a may help explain the epidemiologic predominance of this serotype in the developing world.
Nadav Orr - One of the best experts on this subject based on the ideXlab platform.
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Prevalence of the genes for Shigella enterotoxins 1 and 2 among clinical isolates of Shigella in Israel.
Epidemiology and infection, 2002Co-Authors: M. Yavzori, Dani Cohen, Nadav OrrAbstract:SUMMARY Two enterotoxins, Shigella enterotoxin 1 (SHET1) and Shigella enterotoxin 2 (SHET2) have been recently characterized and are believed to play a role in the clinical manifestation of shigellosis. One hundred and twenty-one isolates of Shigella spp. of 13 different serotypes and variants and 10 isolates of enteroinvasive Escherichia coli (EIEC) isolated in Israel, were examined by polymerase chain reaction for the presence of SHET1 and SHET2 genes. SHETI was only prevalent among isolates of S. flexneri 2a while SHET2 was found in all the serotypes that were tested except for several isolates of S. flexneri Ib that lost their virulence plasmid during storage. In addition, we found that the S. flexneri 2a vaccine strain T-32 Istrati contains the gene encoding for SHETi but not that encoding for SHET2, suggesting that the latter is located within a large deletion occurring in the 140 Mda plasmid of this S. flexneri 2a non-invasive vaccine strain. Shigella species are important pathogens responsible for diarrhoeal diseases and dysentery occurring all over the world. The morbidity and mortality due to shigellosis are especially high among children in developing countries. Travellers from developed to developing regions and soldiers serving under field conditions are also at an increased risk to develop shigellosis. Two enterotoxins have recently been recognized as virulence factors: (a) chromosome encoded Shigella enterotoxin 1 (SHET1) which is present in all Shigella flexneri 2a [1] but rarely found in other Shigella serotypes [2], and (b) Shigella enterotoxin 2 (SHET2) which is located on a large plasmid associated with virulence of Shigella [3]. SHET2 was found in many, but not all, Shigella of different serotypes and also in enteroinvasive Escher
Erik Ekwall - One of the best experts on this subject based on the ideXlab platform.
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Shigellosis in Vietnam: Seroepidemiologic Studies with Use of Lipopolysaccharide Antigens in Enzyme Immunoassays
Clinical Infectious Diseases, 1991Co-Authors: Alf A. Lindberg, Nguyen Chan, Dang Duc Trach, Gunilla Lindberg, Anders Karnell, Kerstin Karlsson, Erik EkwallAbstract:The performance of enzyme immunoassays (EIAs) with use of O-antigen-containing lipopolysaccharides (LPSs) extracted with phenol-water from Shigella dysenteriae type 1, Shigella flexneri serotypes 1a-5b, and Shigella sonnei for determination of the serum antibody responses after onset of bacillary dysentery is reviewed. For the purpose of several studies, serum samples from a total of 175 Vietnamese and 47 Swedish patients, for whom Shigella species had been isolated from fecal specimens, were obtained at various intervals until ≤1 year after the onset of infection
Stephen Baker - One of the best experts on this subject based on the ideXlab platform.
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the genomic signatures of Shigella evolution adaptation and geographical spread
Nature Reviews Microbiology, 2016Co-Authors: Duy Pham Thanh, Kathryn E Holt, Nicholas R Thomson, Stephen BakerAbstract:Shigella spp. are some of the key pathogens responsible for the global burden of diarrhoeal disease. These facultative intracellular bacteria belong to the family Enterobacteriaceae, together with other intestinal pathogens, such as Escherichia coli and Salmonella spp. The genus Shigella comprises four different species, each consisting of several serogroups, all of which show phenotypic similarity, including invasive pathogenicity. DNA sequencing suggests that this similarity results from the convergent evolution of different Shigella spp. founders. Here, we review the evolutionary relationships between Shigella spp. and E . coli, and we highlight how the genomic plasticity of these bacteria and their acquisition of a distinctive virulence plasmid have enabled the development of such highly specialized pathogens. Furthermore, we discuss the insights that genotyping and whole-genome sequencing have provided into the phylogenetics and intercontinental spread of Shigella spp.