Prevalence and characteristics of intimin- and Shiga toxin-producing Escherichia coli from gulls, pigeons and broilers in Finland.
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The role of birds as sources of Shiga toxin-and intimin-producing Escherichia coli was studied. Fecal samples from live gulls (n=86), pigeons (n=33) and broiler chickens (n=199) from 23 flocks were analyzed for stx and eae by PCR. No stx positive samples were detected. In contrast, eae E. coli were highly prevalent among gulls (40%), and was also found in pigeons (7%) and chickens (57% of the flocks contaminated). The eae positive isolates were analyzed genetically and O-serogrouped. One isolate from a pigeon was found to have stx (2f). The isolates of gulls differed from those of pigeons and chickens, and all eae E. coli isolates from birds differed from human pathogenic strains by the lack of EHEC-hlyA and bfp/EAF as well as distribution of O-serogroups. Thus, birds cannot be regarded as important carriers of zoonotic stx or eae E. coli in Finland. (+info)
The mean annual incidence of hemolytic uremic syndrome in persons +info)
Restricted expression of shiga toxin binding sites on mucosal epithelium of mouse distal colon.
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Shiga toxins (Stx) are some of the major virulence factors of enterohemorrhagic Escherichia coli strains such as serotype O157:H7. To explore how Stx might initially gain access to the bloodstream from sites of infection, frozen sections of mouse colon were immunohistochemically examined for binding sites for recombinant binding subunits (Stx1B). Binding sites were selectively expressed on the epithelium in the distal half of the mouse colon, whereas the proximal half did not exhibit any binding sites. In agreement with this observation, we also demonstrated the distal-part-restricted distribution of glycolipids that bind to Stx1B in the mouse colon. For comparison, the binding sites of several control lectins were also examined. Selective binding to the distal part of the colon was not seen with any other control lectins, including Griffonia simplicifolia lectin-I isolectin B4 (GS-I-B4), which shares alpha-galactose specificity with Stx1B. Partial overlapping of the specificities of Stx1B and GS-I-B4 was seen by assay with globotriose-conjugated multivalent ligands. The results indicate that Stx1B is stricter in the recognition of carbohydrate determinants than GS-I-B4 when examined with biological ligands. (+info)
Phenotypic and genotypic characteristics of shiga toxin-producing Escherichia coli strains isolated from children in Sao Paulo, Brazil.
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The biochemical and serological characteristics, virulence properties, and genetic relatedness of Shiga toxin-producing Escherichia coli (STEC) strains isolated in S o Paulo, from April 1989 through March 1990, were determined. This is also the first report on clinic findings of human STEC infections in Brazil. The only three STEC strains identified in that period were lysine decarboxylase negative, belonged to serotype O111ac: non-motile, were Stx1 producers, carried the eae and astA genes, and 2 of them also presented the EHEC-hly sequence. The children carrying STEC were all boys, with less than two years old, and had no previous history of hospitalization. None of them presented blood in stools. Vomiting, cough and coryza were the most common clinical manifestations observed. Although the STEC strains were isolated during summer months, and presented similar phenotypic and genotypic characteristics, carbohydrate fermentation patterns and PFGE analysis suggested that these diarrheal episodes were not caused by a single clone. (+info)
Suppression of NF-kappa B activation and proinflammatory cytokine expression by Shiga toxin-producing Escherichia coli.
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The NF-kappaB family of transcription factors forms one of the first lines of defense against infectious disease by inducing the expression of genes involved in inflammatory and immune responses. In this study, we analyzed the impact of Shiga toxin-producing Escherichia coli (STEC) on the NF-kappaB DNA-binding activity in HeLa cells. After a period of weak initial activation, DNA binding of NF-kappaB was actively suppressed by viable, E. coli secreted protein B (EspB)-secreting STEC. Sustained NF-kappaB activity was observed either using an isogenic mutant lacking EspB or after gentamicin-based killing of STEC after allowing bacterial attachment. These observations indicate that the ability of STEC to cause NF-kappaB activation is suppressed by a translocated bacterial effector protein, which is either EspB itself or requires EspB for delivery into the host cell. We found that STEC, enterohemorrhagic E. coli, and enteropathogenic E. coli all interfere with NF-kappaB activation initiated by TNF-alpha, indicating that suppression of signal-induced NF-kappaB activity is a property common to several attaching and effacing bacteria. As a consequence of NF-kappaB suppression, wild-type STEC induces significantly lower mRNA levels of IL-8, IL-6, and IL-1alpha upon prolonged infection periods compared with bacteria lacking EspB. For IL-8 and IL-6, the suppressive effect was also reflected at the level of cytokine secretion. Suppression of both basal and signal-induced NF-kappaB DNA binding by attaching and effacing-inducing bacteria appears to be an active strategy to counteract host defense responses, thus favoring intestinal colonization by these pathogens. (+info)
Myosin motors and not actin comets are mediators of the actin-based Golgi-to-endoplasmic reticulum protein transport.
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We have previously reported that actin filaments are involved in protein transport from the Golgi complex to the endoplasmic reticulum. Herein, we examined whether myosin motors or actin comets mediate this transport. To address this issue we have used, on one hand, a combination of specific inhibitors such as 2,3-butanedione monoxime (BDM) and 1-[5-isoquinoline sulfonyl]-2-methyl piperazine (ML7), which inhibit myosin and the phosphorylation of myosin II by the myosin light chain kinase, respectively; and a mutant of the nonmuscle myosin II regulatory light chain, which cannot be phosphorylated (MRLC2(AA)). On the other hand, actin comet tails were induced by the overexpression of phosphatidylinositol phosphate 5-kinase. Cells treated with BDM/ML7 or those that express the MRLC2(AA) mutant revealed a significant reduction in the brefeldin A (BFA)-induced fusion of Golgi enzymes with the endoplasmic reticulum (ER). This delay was not caused by an alteration in the formation of the BFA-induced tubules from the Golgi complex. In addition, the Shiga toxin fragment B transport from the Golgi complex to the ER was also altered. This impairment in the retrograde protein transport was not due to depletion of intracellular calcium stores or to the activation of Rho kinase. Neither the reassembly of the Golgi complex after BFA removal nor VSV-G transport from ER to the Golgi was altered in cells treated with BDM/ML7 or expressing MRLC2(AA). Finally, transport carriers containing Shiga toxin did not move into the cytosol at the tips of comet tails of polymerizing actin. Collectively, the results indicate that 1) myosin motors move to transport carriers from the Golgi complex to the ER along actin filaments; 2) nonmuscle myosin II mediates in this process; and 3) actin comets are not involved in retrograde transport. (+info)
Comparison of methods for DNA isolation from food samples for detection of Shiga toxin-producing Escherichia coli by real-time PCR.
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In this study, food samples were intentionally contaminated with Escherichia coli O157:H7, and then DNA was isolated by using four commercial kits. The isolated DNA samples were compared by using real-time PCR detection of the Shiga toxin genes. The four kits tested worked similarly. (+info)
Human milk secretory antibodies against attaching and effacing Escherichia coli antigens.
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Secretory immunoglobulin A (sIgA) is a primary factor responsible for preventing attachment of enteropathogens to gut epithelium in breastfeeding infants. We compared the frequency of sIgA to major surface antigens of enterohemorrhagic Escherichia coli (EHEC) in milk of 123 women from the United States and Mexico to determine whether regional differences existed in the frequency of antibodies to these surface antigens. In both groups of women, milk commonly has sIgA against various EHEC lipopolysaccharides, EspA, EspB, intimin, and less frequently against Shiga toxin. The study suggests that persons living in the United States are exposed to attaching/effacing enteropathogens more frequently than is generally assumed. The low frequency of antibodies to Stx1 (in 12% of Mexican and in 22% of U.S. samples) suggests that the rare appearance of hemolytic uremic syndrome in adults is not due to neutralization of toxin at the gut level. Only anti-EspA is found in most milk samples from both populations of women. EspA may represent a useful target for an immunization strategy to prevent EHEC disease in humans. (+info)