ABSTRACT. The adsorption property of activated charcoal on verotoxin (VT)-producing Escherichia coli (VTEC) was examined using E. coli O157:H7. In the present study, E. coli O157:H7 strains were effectively adsorbed by activated charcoal. Adsorption was dosedependent, and the maximum adsorption occurred within 5 min. At 10 mg of activated charcoal, bacteria tested were completely adsorbed. Activated charcoal also had the capacity to adsorb toxin (verotoxin 2) activity from the bacterial extract. Furthermore, the adsorption efficiency of activated charcoal for the normal bacterial flora in the intestine was assessed using Enterococcus faecium, Bifidobacterium thermophilum, and Lactobacillus acidophilus. Activated charcoal showed lower binding capacity to the normal bacterial flora tested than that to E. coli O157:H7 strains. These results suggest that activated charcoal could be a good adsorbent system for the removal of VTEC and verotoxin.

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The effect of intestinal IgA antibody against the receptor for verotoxin (VT), globotriaosylceramide (Gb3), on VT‐mediated cytotoxicity was examined. Intestinal IgA antibodies against Gb3 were prepared by oral immunization of mice with Gb3 and adjuvant monophosphoryl lipid A (MPL)‐containing liposomes composed of dipalmitoylphosphatidylcholine, dipalmitoylphosphatidylserine and cholesterol (1 : 1 : 2, molar ratio) (PS‐liposome). Oral administration with Gb3 and MPL‐containing PS‐liposome induced significant IgA responses to Gb3 in the intestinal lavage fluid in all mice tested. Furthermore, anti‐Gb3 IgA antibodies in the lavage fluid effectively inhibited the cytotoxicity of VT2 to Vero cells in a dose‐dependent manner. These results suggest that anti‐Gb3 IgA antibodies produced in the intestinal tract, upon oral immunization with Gb3‐containing liposome, function as inhibitors against VT and also indicate the potential usefulness of oral PS‐liposome vaccines containing MPL for the induction of a protective mucosal immune response against intestinal diseases.

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