Adherence of vero cytotoxin-producing Escherichia coli serotype O157:H7 to isolated epithelial cells and brush border membranes in vitro: role of type 1 fimbriae (pili) as a bacterial adhesin expressed by strain CL-49

Abstract

Vero cytotoxin-producing Escherichia coli of the serotype O157-:H7 have recently been associated with sporadic cases and outbreaks of hemorrhagic colitis and with the hemolytic-uremic syndrome. E. coli O157:H7 strains adhere to human epithelial cells in tissue culture and to the intestine of orally infected rabbits. To determine whether E. coli O157:H7 adhere to normal post-natal human epithelial cells, we isolated buccal epithelial cells from healthy adult volunteers and isolated ileal enterocytes and colonocytes from histologically normal margins of surgical resection specimens. Apical brush border membranes from the distal ileum and colonocytes of the proximal colon were also prepared from post-weaning rabbits. Binding of five E. coli O157:H7 strains to epithelial cells and brush border membranes was determined by two complementary methods: firstly, under phase contrast microscopy and secondly, by quantitating adherence of radiolabelled bacteria to substrates that were bound to polystyrene microtiter wells. Under incubation conditions used previously to document in vitro adherence of other diarrheagenic E. coli, only the one type-1 fimbriated E. coli O157:H7 strain, designated CL-49, adhered to isolated human and rabbit epithelial cells. In contrast, binding of 4 non-type-1 fimbriated O157:H7 strains could not be demonstrated. Adherence of the fimbriated E. coli O157:H7 strain was saturable and varied with pH and temperature of the incubation medium. Adherence of bacteria to rabbit ileal brush borders was mediated by binding of bacteria to alpha-linked mannosyl residues present on surface glycoproteins.(ABSTRACT TRUNCATED AT 250 WORDS)