An in-vitro model for studying the interaction of Escherichia coli O157 : H7 and other enteropathogens with bovine primary cell cultures

Sections of kidney, trachea, ileum, colon, rectum and rumen were removed at post mortem from a neonatal calf and, with the exception of the rumen, pri mary cell lines were established for each of the cell types. The adherence of enterohaemorrhagic Escherichia coli (EHEC) serotype O157:H7, enteropatho genic E. coli (EPEC) serotype O111, E. coli K12 (a laboratory adapted non-p athogenic strain) and Salmonella enterica serotype Typhimurium was assayed on each cell type. For all adherence assays on all cell lines, EHEC O157:H7 adhered to a significantly greater extent than the other bacteria. S. Typh imurium and EPEC O111 adhered to a similar extent to one another, whereas E . coli K12 was significantly less adherent by 100-fold. In all cell types, > 10% of adherent S. Typhimurium bacteria invaded, whereas c. 0.01-0.1% of adherent EHEC O157:H7 and EPEC O111 bacteria invaded, although they are reg arded as non-invasive. EHEC O157 generated actin re-arrangements in all cel l types as demonstrated by fluorescent actin staining (FAS) under densely p acked bacterial micro-colonies. EPEC O111 readily generated the localised a dherent phenotype on bovine cells but generated only densely packed micro-c olonies on HEp-2 cells. The intensity of actin re-arrangements induced in b ovine cells by EPEC O111 was less than that induced by EHEC O157:H7. The in timate attachment on all cell types by both EHEC O157:H7 and EPEC O111 was clearly demonstrated by scanning electron microscopy.