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Eradication of H. pylori infection markedly changes the natural history of peptic ulcer in patients with duodenal or gastric ulcer. Most peptic ulcers associated with H. pylori infection are curable.

An enterotoxin-producing strain of Escherichia coli isolated from a case of cholera-like diarrhea (E. coli strain H-10407) was found to possess a surfaceassociated colonization factor. Colonization was manifested as the ability of small inocula (105 bacteria) to attain large (10w) populations in the infant rabbit intestine with a concomitant diarrheal response. A laboratory-passed derivative of E. coli H-10407, designated H-10407-P, failed to exhibit an increase in population in the infant rabbit and also failed to induce diarrhea. Cell-free culture supernatant fluids of E. coli H-10407 and H-10407-P produced equivalent enterotoxic responses in infant and in adult rabbits. Specific anti-colonization factor antiserum was produced by adsorbing hyperimmune anti-H-10407 serum with both heat-killed and living cells of E. coli H-10407-P. This specific adsorbed serum protected infant rabbits from challenge with living E. coli H-10407 although the serum did not possess bactericidal activity. The anti-colonization factor serum did not agglutinate a strain of E. coli K-12 possessing the K88 colonization factor peculiar to E. coli enterotoxigenic for swine. By electron microscopy it was demonstrated that E. coli H-10407, but not H-10407-P, possessed pilus-like surface structures which agglutinated with the specific adsorbed (anti-colonization factor) antiserum. E. coli H-10407 possessed three species of plasmid deoxyribonucleic acid, measuring 60 x 10X, 42 x 106, and 3.7 x 10' daltons, respectively. E. coli H-10407-P possessed only the 42 x 106and the 3.7 x 106-dalton plasmid species. Spontaneous loss of the specific H-10407 surface-associated antigen was accompanied by loss of the 60 x 106-dalton species of

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Enterotoxigenic Escherichia coli (ETEC) of several different serotypes isolated from adults with diarrhea and known to possess the colonization factor antigen (CFA) were found to cause mannose-resistant hemagglutination (HA) of human group A erythrocytes. CFA-negative E. coli isolated during the same study did not possess the mannose-resistant hemagglutinin, although some non-ETEC, CFA-negative isolates did exhibit mannose-sensitive HA activity. The mannoseresistant hemagglutinin of ETEC was found to possess many characteristics previously associated with CFA, which is a surface-associated fimbriate heatlabile antigen, and the functionally and morphologically similar K88 and K99 antigens of animal-specific ETEC. Mannose-resistant HA and CFA titers were maximal when ETEC cells were grown on an agar medium (CFA agar) composed primarily of 1% Casamino Acids and 0.15% yeast extract, pH 7.4. Neither CFA nor HA were produced at a growth temperature of 18°C; HA was completely inhibited by pretreatment of CFA-positive cells with the anti-CFA serum. The mannose-resistant hemagglutinin was lost spontaneously and simultaneously with CFA when clinical ETEC isolates were passaged on artificial medium in the laboratory, indicating plasmid control of both entities. The mannose-resistant hemagglutinin of ETEC was shown to be thermolabile, i.e., sensitive to heating at 65°C, as was the CFA. Also, there was correlation between possession of CFA, as detected serologically and by demonstration of biological activity (adherence in the infant rabbit small intestine), presence of CFA-type fimbriae, and the ability of various E. coli isolates to cause mannose-resistant HA of human group A erythrocytes. These results indicate that the mannose-resistant HA of ETEC is another manifestation of CFA.

Enterotoxigenic Escherichia coli (ETEC) belonging to serogroups O6 and O8 do not possess the H-10407-type colonization factor antigen (CFA/I). However, these frequently isolated ETEC were found to possess a second and distinct heat-labile surface-associated colonization factor antigen, termed CFA/II. Whereas CFA/I mediates mannose-resistant hemagglutination of human group A erythrocytes, CFA/II does not. CFA/II mediates mannose-resistant hemagglutination of bovine erythrocytes, and mannose-resistant hemagglutination is rapid only at reduced temperature (4°C). Because CFA/II, like CFA/I, is spontaneously lost by many ETEC isolates in the laboratory, it was possible to produce specific anti-CFA/II serum by preparing antiserum against living cells of a prototype strain (PB-176) and adsorbing this serum with living and heat-treated cells of its CFA/II-negative derivative strain PB-176-P. This serum, which neutralized the colonization factor activity of CFA/II-positive strains in infant rabbits, was employed to confirm the presence of CFA/II on ETEC which exhibited mannose-resistant hemagglutination of bovine but not human erythrocytes. CFA/II, like CFA/I, mediates adherence of the bacteria to the mucosal surface of the small intestine, as demonstrated by indirect immunofluorescence. CFA/II appears to be an important virulence factor for humans since CFA/II-positive ETEC are frequently isolated from diarrhea cases, particularly travelers' diarrhea, in Mexico; these ETEC were not uncommon in a collection of isolates from Bangladesh. The O6:H16 strain of ETEC responsible for an outbreak of diarrhea in the United States was also shown to be CFA/II positive. CFA/I and CFA/II were never found on the same serotypes of ETEC, but 98% of the heat-stable and heat-labile enterotoxin-producing ETEC belonging to the frequently isolated serogroups O6, O8, O15, O25, O63, and O78 were positive for either CFA/I or CFA/II.

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