The prevalence of verotoxins, Escherichia coli O157:H7, and Salmonella in the feces and rumen of cattle at processing.
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Fecal samples collected from cattle at processing during a 1-year period were tested for verotoxins (VT1, VT2), Escherichia coli O157:H7, and Salmonella. Verotoxins were detected in 42.6% (95% CI, 39.8% to 45.4%), E. coli O157:H7 in 7.5% (95% CI, 6.1% to 9.1%), and Salmonella in 0.08% (95% CI, 0.004% to 0.5%) of the fecal samples. In yearling cattle, the median within-lot prevalence (percentage of positive samples within a lot) was 40% (range, 0% to 100%) for verotoxins and 0% for E. coli O157:H7 (range, 0% to 100%) and Salmonella (range, 0% to 17%). One or more fecal samples were positive for verotoxins in 80.4% (95% CI, 72.8% to 86.4%) of the lots of yearling cattle, whereas E. coli O157:H7 were detected in 33.6% (95% CI, 26.0% to 42.0%) of the lots. In cull cows, the median within-lot prevalence was 50% (range, 0% to 100%) for verotoxins and 0% (range, 0% to 100%) for E. coli O157:H7 and Salmonella (range, 0% to 0%). Verotoxins were detected in one or more fecal samples from 78.0% (95% CI, 70.4% to 84.2%) of the lots of cull cows, whereas E. coli O157:H7 were detected in only 6.0% (95% CI, 3.0% to 11.4%) of the lots of cull cows. The prevalence of verotoxins in fecal samples was lower in yearling cattle than in cull cows, whereas the prevalence of E. coli O157:H7 in fecal samples was higher in yearling cattle than in cull cows. The prevalence of E. coli O157:H7 in fecal samples was highest in the summer months. Rumen fill, body condition score, sex, type of cattle (dairy, beef), and distance travelled to the plant were not associated with the fecal prevalence of verotoxins or E. coli O157:H7. The prevalence of verotoxins in fecal samples of cull cows was associated with the source of the cattle. It was highest in cows from the auction market (52%) and farm/ranch (47%) and lowest in cows from the feedlot (31%). In rumen samples, the prevalence of verotoxins was 6.4% (95% CI, 4.2% to 9.4%), and it was 0.8% (95% CI, 0.2% to 2.3%) for E. coli O157:H7, and 0.3% (95% CI, 0.007% to 1.5%) for Salmonella. (+info)
The surveillance of vero cytotoxin-producing Escherichia coli O157 in Wales, 1990 to 1998.
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Population-based surveillance for Vero cytotoxin-producing Escherichia coli (VTEC) O157 has been carried out in Wales since 1990. The annual incidence has remained stable during the 9-year period (mean: 1.6 cases per 100,000 population); the rate is highest in children younger than 5 years of age. Blood in the stool is reported in fewer than half the cases, indicating the importance of screening all fecal specimens for VTEC O157. (+info)
A reverse-sandwich enzyme-linked immunosorbent assay for verocytotoxin 1 and 2 antibodies in human and bovine sera.
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A reverse-sandwich enzyme-linked immunosorbent assay (ELISA), in which an antibody is sandwiched by antigens, was established for the titration of antibodies to verocytotoxins (VT) in human and animal sera. This assay has two advantages over a conventional indirect ELISA: (i) higher specificity and sensitivity and (ii) the ability to comparably titrate antibodies from different species. The VT1 (Shiga-like toxin 1) antibody-positive rates were 5% in 202 normal adult humans and 99% in 93 normal cattle at a dairy farm. This ELISA is most suitable for seroepidemiologic studies of infections with VT-producing Escherichia coli in humans and various animal species. (+info)
Molecular characterisation of verocytotoxin-producing Escherichia coli of serogroup O111 from different countries.
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A collection of epidemiologically unrelated verocytotoxin (VT)-producing Escherichia coli (VTEC) strains of serogroup O111 isolated from human patients and cattle with diarrhoeal disease in five different countries were characterised by determination of their VT genotypes, the presence of other virulence factors such as the intimin-coding eae gene and the enterohaemorrhagic E. coli (EHEC) plasmid, and their antibiotic susceptibility patterns. The genetic relatedness among isolates was evaluated by genomic DNA fingerprinting techniques such as restriction fragment length polymorphism analysis of ribosomal RNA genes (ribotyping) and pulsed-field gel electrophoresis. The results indicated that the VTEC O111 examined belong to two distinct clonal lineages. The first group was constituted mainly of non-motile, eae-positive, EHEC plasmid-positive isolates from both man and cattle. The second lineage was represented by an O111:H2 epidemic strain, isolated during an outbreak of haemolytic uraemic syndrome in France and exhibiting an unusual combination of virulence factors: VT production and aggregative adhesion to HEp-2 cells associated with an enteroaggregative E. coli (EAEC) plasmid. (+info)
Inhibition of neutrophil apoptosis by verotoxin 2 derived from Escherichia coli O157:H7.
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In order to evaluate the pathological role of verotoxin 2 (VT2), we investigated the effects of VT2 on neutrophil apoptosis in vitro. The results showed that VT2 caused a significant delay in spontaneous neutrophil apoptosis and that the effect was abrogated by a protein kinase C inhibitor. These data indicate that longer survival of neutrophils may aggravate neutrophil-mediated tissue damage in VT2-associated diseases. (+info)
Chromosome of the enterohemorrhagic Escherichia coli O157:H7; comparative analysis with K-12 MG1655 revealed the acquisition of a large amount of foreign DNAs.
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A complete Xba I and Bln I cleavage map was constructed for the chromosome of an enterohemorrhagic Escherichia coli (EHEC) O157:H7 strain isolated from an outbreak in Sakai City, Japan, in 1996. A comparative chromosome analysis with E. coli K-12 strain MG1655 was made. The EHEC chromosome was approximately 5600 kb in length, 1 Mb larger than that of MG1655. Despite the marked difference in chromosome length, the location and direction of seven rRNA operons of the EHEC strain were similar to those for MG1655. Overall organization of genes common in both strains is also highly conserved. Chromosome expansion was observed throughout the EHEC chromosome, albeit in an uneven manner. A large portion of the chromosome enlargement was observed in the region surrounding the replication terminus, particularly in a segment containing the terA locus. Sample sequencing of 3627 random shotgun clones suggested the presence of approximately 1550 kb strain-specific DNAs on the EHEC chromosome, most of which are likely to be of foreign origin. (+info)
Complete nucleotide sequence of the prophage VT2-Sakai carrying the verotoxin 2 genes of the enterohemorrhagic Escherichia coli O157:H7 derived from the Sakai outbreak.
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The enterohemorrhagic Escherichia coli (EHEC) O157:H7 strain RIMD 0509952, derived from an outbreak in Sakai city, Japan, in 1996, produces two kinds of verotoxins, VT1 and VT2, encoded by the stx1 and stx2 genes. In the EHEC strains, as well as in other VT-producing E. coli strains, the toxins are encoded by lysogenic bacteriophages. The EHEC O157:H7 strain RIMD 0509952 did not produce plaque-forming phage particles upon inducing treatments. We have determined the complete nucleotide sequence of a prophage, VT2-Sakai, carrying the stx2A and stx2B genes on the chromosome, and presumed the putative functions of the encoded proteins and the cis-acting DNA elements based on sequence homology data. To our surprise, the sequences in the regions of VT2-Sakai corresponding to the early gene regulators and replication proteins, and the DNA sequences recognized by the regulators share very limited homology to those of the VT2-encoding 933W phage carried by the EHEC O157:H7 strain EDL933 reported by Plunkett et al. (J. Bacteriol., p1767-1778, 181, 1999), although the sequences corresponding to the structural components are almost identical. These data suggest that these two phages were derived from a common ancestral phage and that either or both of them underwent multiple genetic rearrangements. An IS629 insertion was found downstream of the stx2B gene and upstream of the lysis gene S, and this might be responsible for the absence of plaque-forming activity in the lysate obtained after inducing treatments. (+info)
A mutant Shiga-like toxin IIe bound to its receptor Gb(3): structure of a group II Shiga-like toxin with altered binding specificity.
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BACKGROUND: Shiga-like toxins (SLTs) are produced by the pathogenic strains of Escherichia coli that cause hemorrhagic colitis and hemolytic uremic syndrome. These diseases in humans are generally associated with group II family members (SLT-II and SLT-IIc), whereas SLT-IIe (pig edema toxin) is central to edema disease of swine. The pentameric B-subunit component of the majority of family members binds to the cell-surface glycolipid globotriaosyl ceramide (Gb(3)), but globotetraosyl ceramide (Gb(4)) is the preferred receptor for SLT-IIe. A double-mutant of the SLT-IIe B subunit that reverses two sequence differences from SLT-II (GT3; Gln65-->Glu, Lys67-->Gln, SLT-I numbering) has been shown to bind more strongly to Gb(3) than to Gb(4). RESULTS: To understand the molecular basis of receptor binding and specificity, we have determined the structure of the GT3 mutant B pentamer, both in complex with a Gb(3) analogue (2.0 A resolution; R = 0.155, R(free) = 0.194) and in its native form (2.35 A resolution; R = 0.187, R(free) = 0.232). CONCLUSIONS: These are the first structures of a member of the medically important group II Shiga-like toxins to be reported. The structures confirm the previous observation of multiple binding sites on each SLT monomer, although binding site 3 is not occupied in the GT3 structure. Analysis of the binding properties of mutants suggests that site 3 is a secondary Gb(4)-binding site. The two mutated residues are located appropriately to interact with the extra betaGalNAc residue on Gb(4). Differences in the binding sites provide a molecular basis for understanding the tissue specificities and pathogenic mechanisms of members of the SLT family. (+info)