title: In vitro model of adhesion and invasion by Bacillus piliformis.
abstract: An in vitro model of Bacillus piliformis infection was developed to investigate the mechanisms of adhesion and internalization of this obligate intracellular bacterium. Adhesion and internalization events were examined by electron microscopic evaluation of infected Caco-2 cell monolayers. A few bacteria were identified in apical surface invaginations and in vacuoles subjacent to the apical surface, whereas the majority of bacteria were observed free within the cytoplasm, suggesting that B. piliformis entered epithelial cells via a phagocytic process and rapidly escaped the phagosome. To confirm that host cell phagocytosis was involved in entry of B. piliformis into mammalian cells, Intestine 407 cells were treated with the phagocytic inhibitor cytochalasin D, infected with B. piliformis, and evaluated for bacterial internalization by double-fluorescence labeling. The results showed decreased intracellular bacteria, suggesting that internalization was dependent on host cell microfilament function. To examine the role of B. piliformis in internalization, growth of live and Formalin-killed bacteria was compared. Dead bacteria were not internalized, suggesting that B. piliformis actively participates in internalization. B. piliformis appears to enter host cells by a bacterially directed phagocytic process. The in vitro system described should prove invaluable in further investigations of B. piliformis pathogenic mechanisms.
authors.affiliation: Department of Veterinary Pathology, College of Veterinary Medicine, University of Missouri, Columbia, Missouri 65211.
authors.forename: C L
authors.initials: CL
authors.lastname: Franklin
authors.forename: D A
authors.initials: DA
authors.lastname: Kinden
authors.forename: P L
authors.initials: PL
authors.lastname: Stogsdill
authors.forename: L K
authors.initials: LK
authors.lastname: Riley
mesh_terms: D008841:Actin Cytoskeleton / Q000502:physiology; D016863:Bacillaceae Infections / Q000276:immunology* / Q000382:microbiology; D001407:Bacillus / Q000254:growth & development / Q000472:pathogenicity*; D001422:Bacterial Adhesion; D015638:Cytochalasin D / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006801:Humans; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000166:cytology / Q000382:microbiology*; D008854:Microscopy, Electron; D014407:Tumor Cells, Cultured
chemical_list: D015638:Cytochalasin D