Adherent Escherichia coli in colorectal mucosal biopsies: A histological and ultrastructural evaluation.

Background: Colorectal mucosal biopsies occasionally demonstrate the presence of bacteria adherent to the epithelium. This study evaluated the histological and ultrastructural correlates of such bacterial adherence. Materials and Methods: Rectal mucosal biopsies from eight patients in whom histopathological examination of biopsies had earlier demonstrated adherent bacteria were examined by electron microscopy and by bacterial culture. Colorectal biopsies of 69 patients with adherent bacteria detected histologically were retrospectively evaluated for histological changes at sites proximal and distant to adherent bacteria. Results: Escherichia coli of different serogroups were isolated from 7 of 8 rectal biopsies demonstrating bacterial adherence. All isolates showed diffuse or focal adherence to HEp-2 cell monolayers. Ultrastructural changes noted included microvillus damage, pedestal formation, actin web condensation, and protrusions of the apical cytoplasm of epithelial cells into the lumen towards the bacteria. Histological changes noted at light microscopy included reduction in epithelial cell height, focal epithelial cell degeneration, cryptitis and neutrophil infiltration at sites of bacterial adherence whereas these were usually absent at sites distant to adherent bacteria. Bacterial adherence was noted more often in biopsies from Crohn's disease patients than in patients without this diagnosis (P < 0.001). Conclusion: Adherent Escherichia coli in colorectal biopsies were associated with focal epithelial damage and showed an association with Crohn's disease.

Cytoskeletal changes during poliovirus infection in an intestinal cell line.

BACKGROUND & OBJECTIVES: Although polioviral replication has been extensively studied, cytoskeletal changes in the host cell during poliovirus replication have not been extensively investigated. We studied the ultrastructural and cytoskeletal changes in host cells during poliovirus infection. METHODS: Fluorescence staining of filamentous actin with a fluorescein-isothiocynate labelled mycotoxin, in the absence and presence of microfilament inhibitors cytochalasins B and D, and electron microscopy were used to investigate the role and fate of actin microfilaments during poliovirus infection, morphogenesis and release in an intestinal cell line, HRT-18. RESULTS: At 10 h post-infection, fluorescence staining of actin showed focal areas of fluorescence in the cytoplasm. By 16 h, these became more prominent and increased in number, and by 18-22 h they coalesced to enclose areas of the cytoplasm. These changes in the actin profile were confirmed by electron microscopy, where small actin bundles appeared in association with vesicles, increased in size, number and thickness, enclosed areas of cytoplasm with numerous vesicles and were finally seen in association with crystalline arrays of virus near the periphery of the cells. The addition of microfilament inhibitors cytochalasins B and D, after the initial period of adsorption resulted in complete inhibition of changes in the actin profile and of viral release, indicating that microfilament inhibitors prevented both polymerization of actin and movement of the virus within the cell. INTERPRETATION & CONCLUSION: In poliovirus infection, both intracellular movement and release of virus appear to be related to cytoskeletal changes, particularly involving actin microfilaments.