Special O:K:H serotypes among enterotoxigenic E. coli strains from diarrhea in adults and children. Occurrence of the CF (colonization factor) antigen and of hemagglutinating abilities.

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H serotypes previously found to be prevalent among a number of toxigenic strains from several geographic areas were examined for polysaccharide K antigen type. Members of each O:H serotype had the same type of K antigen and were found to be characterized by a certain fermentation pattern. Some O:H serotypes had no K antigen. The serofermentative types defined were: 06:K15:H16, 08:K40:H9, 015:H11, 025:K7:H42, 025:K98:H-, 078:H11, 078:H12, and 0149:H10. Some strains of the last-mentioned serotype, which were suspected of having caused a food-borne infection, had K88. This serotype belongs to the group of strains causing diarrhea in swine. The surface antigen (CF) described as a colonization factor [5] was demonstrated in 078:H-, 078:H11, and 078:H12 strains; but not in any strain of the other serotypes nor in any of 248 strains belonging to 078 but not isolated from cases of human diarrhea. Presence of the CF antigen was correlated with presence of a mannose-resistant ability to cause agglutination of human red cells. Behavior of the other serotypes as regards hemagglutinating abilities was examined and 025:K7:H42 strains were found to be very similar to the 078 strains in this respect.