Protective effect of Lactobacillus casei strain Shirota on Shiga toxin-producing Escherichia coli O157:H7 infection in infant rabbits. (9/321)

We examined colonization patterns of Shiga toxin-producing Escherichia coli (STEC), concentrations of Shiga toxins (Stxs) and specific immunoglobulin A (lgA) against Stxs and STEC bacterial cell surface antigen in various portions of the gastrointestinal tract in an infant rabbit infection model. After inoculation of 3-day-old infant rabbits with STEC strain 89020087 at low doses (approximately 10(3) CFU/body), numbers of colonizing STEC bacteria and concentrations of Stxs in the intestine increased dramatically and the animals developed diarrhea within a couple of days after infection. Daily administration of Lactobacillus casei from the day of birth dramatically decreased the severity of diarrhea and lowered STEC colonization levels in the gastrointestinal tract 100-fold day 7 after infection. Both Stx1 and Stx2 concentrations in the intestines and histological damage to the intestinal mucus induced by STEC infection were decreased by the administration of L. casei. Examination of the concentrations of volatile fatty acids and pH of the intestinal contents revealed that the protective effect of L. casei administration against STEC infection was not due to fermented products such as lactic acid in the gastrointestinal tract. Administration of L. casei increased levels of lgAs against Stx1, Stx2, and formalin-killed STEC cells in the colon approximately two-, four-, and threefold, respectively, compared with those of the untreated controls by day 7 after infection. These results suggest that administration of L. casei strain Shirota enhances the local immune responses to STEC cells and Stxs and leads to elimination of STEC and thus decreases Stx concentrations in the intestines.  (+info)

Oral administration of formaldehyde-killed recombinant bacteria expressing a mimic of the Shiga toxin receptor protects mice from fatal challenge with Shiga-toxigenic Escherichia coli. (10/321)

Gastrointestinal disease caused by Shiga toxin-producing Escherichia coli (STEC) is frequently complicated by life-threatening toxin-induced systemic sequelae, including the hemolytic uremic syndrome. We previously constructed a recombinant bacterium displaying a Shiga toxin receptor mimic on its surface which neutralized Shiga toxins with very high efficiency. Moreover, oral administration of the live bacterium completely protected mice from challenge with virulent STEC. In this study, we investigated the protective capacity of formaldehyde-killed receptor mimic bacteria, as these are likely to be safer for administration to humans. The killed bacteria completely protected STEC-challenged mice when administered three times daily; incomplete protection was achieved using two doses per day. Commencement of therapy could be delayed for up to 48 h after challenge without diminishing protection, depending on the virulence of the challenge strain. Thus, administration of this agent early in the course of human STEC disease may prevent progression to life-threatening complications.  (+info)

Tumor necrosis factor alpha increases human cerebral endothelial cell Gb3 and sensitivity to Shiga toxin. (11/321)

Hemolytic uremic syndrome (HUS) is associated with intestinal infection by enterohemorrhagic Escherichia coli strains that produce Shiga toxins. Globotriaosylceramide (Gb3) is the functional receptor for Shiga toxin, and tumor necrosis factor alpha (TNF-alpha) upregulates Gb3 in both human macrovascular umbilical vein endothelial cells and human microvascular brain endothelial cells. TNF-alpha treatment enhanced Shiga toxin binding and sensitivity to toxin. This upregulation was specific for Gb3 species containing normal fatty acids (NFA). Central nervous system (CNS) pathology in HUS could involve cytokine-stimulated elevation of endothelial NFA-Gb3 levels. Differential expression of Gb3 species may be a critical determinant of Shiga toxin toxicity and of CNS involvement in HUS.  (+info)

Human neutrophils and their products induce Shiga toxin production by enterohemorrhagic Escherichia coli. (12/321)

The Shiga toxins (Stx) are critical virulence factors for Escherichia coli O157:H7 and other serotypes of enterohemorrhagic E. coli (EHEC). These potent toxins are encoded in the genomes of temperate lambdoid bacteriophages. We recently demonstrated that induction of the resident Stx2-encoding prophage in an O157:H7 clinical isolate is required for toxin production by this strain. Since several factors produced by human cells, including hydrogen peroxide (H2O2), are capable of inducing lambdoid prophages, we hypothesized that such molecules might also induce toxin production by EHEC. Here, we studied whether H2O2 and also human neutrophils, an important endogenous source of H2O2, induced Stx2 expression by an EHEC clinical isolate. Both H2O2 and neutrophils were found to augment Stx2 production, raising the possibility that these agents may lead to prophage induction in vivo and thereby contribute to EHEC pathogenesis.  (+info)

Phenotypic and genotypic characteristics of Escherichia coli strains of non-enteropathogenic E. coli (EPEC) serogroups that carry EAE and lack the EPEC adherence factor and Shiga toxin DNA probe sequences. (13/321)

This study was conducted to characterize the virulence potential of 59 Escherichia coli strains carrying EAE and lacking the enteropathogenic E. coli adherence factor and Shiga toxin probe sequences. In hybridization studies, all strains carried the locus of enterocyte effacement (LEE)-associated DNA sequences. Of the other 15 virulence DNA sequences tested, HLY was the most frequent (44.1%); 17 combinations of these sequences were found, but strains carrying EAE only (EAE profile) were the most frequent (35.6%). Except for 1 cytodetaching strain, all others adhered to HeLa and Caco-2 cells, most of which (approximately 75.0%) showed variations of the localized adherence pattern. Actin accumulation was detected in 75.9% of the nondetaching strains. Most strains had LEE, probably inserted in pheU (49.2%), and presented a nontypeable intimin (83.1%). Translocated intimin receptor-derived DNA sequences correlated with enteropathogenic and enterohemorrhagic E. coli in 61.0% and 32.0% of the strains, respectively. Thirty-five different serotypes were found. Only strains with the EAE profile were associated with diarrhea (P=.039).  (+info)

Genomic fingerprinting of shigatoxin-producing Escherichia coli (STEC) strains: comparison of pulsed-field gel electrophoresis (PFGE) and fluorescent amplified-fragment-length polymorphism (FAFLP). (14/321)

For epidemiological studies of shigatoxin-producing Escherichia coli (STEC) infections, rapid, reproducible and highly discriminative methods are required. In this study, we examined the performance of the fluorescent amplified-fragment-length polymorphism (FAFLP) technique for epidemiological fingerprinting of STEC isolates and compared it to the acknowledged fingerprinting method pulsed-field gel electrophoresis (PFGE). A total of 88 STEC isolates, including 82 of serotype O157:H7 or O157:H-, were subjected to fingerprinting by both PFGE and FAFLP. The isolates included sporadic and epidemiologically related strains of both animal and human origin from widespread geographical locations. The FAFLP fingerprint patterns confirmed the clonal nature of STEC O157 strains. Among the 82 O157:H7/H- isolates belonging to 49 distinct groups of epidemiological unrelated isolates, 24 FAFLP profiles and 51 PFGE patterns were obtained. Thus, PFGE had a higher discriminatory power than FAFLP and overall correlated better to available epidemiological data. Consequently, the PFGE technique remains the method of choice in epidemiological investigations of STEC infections.  (+info)

Phage types and genotypes of Shiga toxin-Producing Escherichia coli O157 in Finland. (15/321)

This study examined Shiga toxin-producing Escherichia coli (STEC) O157, using phage typing, pulsed-field gel electrophoresis, and typing of Shiga toxin variant genes by PCR with restriction fragment length polymorphism in an epidemiological survey of STEC O157 isolated from humans in Finland between 1990 and 1999.  (+info)

A comparative study of the immunity region of lambdoid phages including Shiga-toxin-converting phages: molecular basis for cross immunity. (16/321)

Comparison of eight lambdoid phages, including three Shiga-toxin converting phages, has been carried out with respect to the immunity region, especially the recognition helices of their repressor and CRO proteins on the one hand, and operator sequences on the other. Some as yet unassigned components of the regulatory circuits have been inferred by computer search. The cross immunity phenomenon shown by phages VT2-Sa and lambda is explained on the basis of similarity in their sequences. In addition, the similarity of 933W and HK022 in the sequences of their recognition helices of repressor and CRO, on the one hand, and operators, on the other, has led us to predict that they will have identical or similar immunity specificity. This homology has enabled us also to locate the OL (and consequently PL) of phage 933W that has been thought to be non-existent.  (+info)