Some Shiga toxin-producing Escherichia coli (STEC) strains, enterohemorrhagic E. coli strains, are food-borne pathogens which evoke life-threatening diseases in humans (26). Cattle and other ruminants can shed STEC for long periods and are a major reservoir for zoonotic STEC (6,61,70,72). Emerging human STEC infections make the reduction of STEC shedding by reservoir species a current challenge in veterinary public health.Several lines of evidence indicate that STEC adherence to bovine intestinal epithelial cells is essential for long-term STEC colonization of ruminants. Within hours after oral infection, STEC O157:H7 can be detected throughout the gastrointestinal tract, including the rumen, of cattle (6, 18). As early as 4 days after inoculation, STEC strains colonize epithelial cells in the ileum, cecum, colon, rectum, and gall bladder in weaned calves (8, 59, 62). STEC O157:H7 strains principally colonize the rectoanal junction of weaned calves and older cattle (10, 33, 44), but O157:H7 colonization also can occur at other sites of the bovine intestinal tract (8,23,55). The ability of the majority of bovine STEC isolates to intimately attach to cells and rearrange the actin cytoskeleton (attachingand-effacing [AE] lesions) (71) may facilitate adherence to the intestinal epithelium (5, 9, 44). Signature-tagged mutagenesis studies showed that factors not involved in AE lesion formation further support STEC colonization of the bovine intestinal epithelium (11,68). The duration of STEC shedding correlates with epithelial cell turnover in the bovine intestine (35). Vaccination strategies directed against proteins involved in STEC adherence to the bovine intestinal mucosa have been successful in reducing STEC O157:H7 infection in cattle (49,50,52,67).Other STEC factors also may influence the duration of colonization. Recent studies suggest that STEC suppresses the bovine host's immune response, limits mucosal inflammation, and maintains intestinal homeostasis. Lymphostatin (2) and Shiga toxin 1 (Stx1) (39) block the proliferation of bovine lymphocytes in vitro. Stx1 alters the cytokine response of bovine intraepithelial lymphocytes (42), cells that are scattered within the epithelial layer and are affected in vivo by Stx1 from STEC strains that do not colonize next to organized lymphoid tissues (38). Some STEC O157:H7 strains exhibit a tropism for the follicle-associated epithelium of Peyer's patches in the bovine intestine (51) and may release modulating factors adjacent to induction sites of the immune response. Development of a cellular immune response against STEC antigens is significantly delayed in calves inoculated with Stx2-producing E. coli O157:H7 compared to that of calves inoculated with a nontoxigenic O157:H7 strain (22). Immune-modulating STEC factors are potential targets for future strategies aimed at reducing STEC shedding in cattle, but their mode of action in the bovine intestine is only partially understood.Stx proteins are potent 1A:5B-structured cytotoxins with RNA N-glycosidase activity tha...

The first merogony of Eimeria bovis takes place in lymphatic endothelial cells of the ileum, resulting in the formation of macromeronts up to 250 microm. In this study, we investigated the host cell cytoskeleton (actin filaments, microtubules, spectrin, vimentin intermediate filaments) associated with parasitic development in vitro by confocal laser scanning microscopy (CLSM) using primary bovine umbilical vein endothelial cells (BUVEC) and bovine spleen lymphatic endothelial cells (BSLEC) as host cells. No prominent changes in the host cell cytoskeleton were detected 1-3 days after E. bovis sporozoite invasion. With ongoing meront maturation a significant increase in microtubules and actin filaments close to the parasitophorous vacuole (PV) was found. Mature macromeronts within the PV were completely enclosed by these cytoskeletal elements. Our findings suggest, that in order to guarantee the survival of the host cell on the enlargement of macromeronts, E. bovis needs not only to augment but also to rearrange its cytoskeletal system.

Four commercially available serological assays for the detection of IgM phase II antibodies in patients with acute Q fever infection were compared using a panel of 23 serum samples from patients with acute Q fever and 88 control sera from blood donors.

Rickettsiae are able to spread within infected cell mono-layers by modifying intra-cellular actin formations. The study analyzes whether a visualization of actin modifications in addition to specific immuno-fluorescence staining of rickettsiae might facilitate the proof of rickettsial growth in cell culture. Cell mono-layers of Vero E6 und BGM cells were infected with Rickettsia honei. Intra-cellular actin was fluorescence stained with TRITC-(tetra-methyl-5,6-isothiocyanate)-labeled phalloidin in addition to specific immuno-fluorescence staining of rickettsiae with FITC-(fluorescein-isothiocyanate)-labeled antibodies. DNA of bacteria and cells was counter-stained with DAPI (4´,6-diamino-2-phenyl-indole). Cell cultures infected with Vaccinia virus were used as positive controls, cell cultures infected with Coxiella burnetii as negative controls. High concentrations of R. honei are necessary to demonstrate characteristic modifications of the intra-cellular actin. This effect is more pronounced in Vero E6 cells than in BGM cells. Actin staining with phalloidin is not suited for an early proof of rickettsial growth in cell culture but may confirm unclear findings in specific immuno-fluorescence staining in case of sufficient bacterial density.