U.S. Department of Defense


Date of this Version



The Journal of Infectious Diseases (1985), 152(3), p. 550-559.


Isolates of the most common 0 serogroups of enteropathogenic Escherichia coli (EPEC) associated with infant diarrhea (designated class I) adhere to Hep-2 cells; the genes for this adhesin, termed EPEC adherence factor (EAF), are located on plasmids 50-70 MDa in size. Volunteers ingested 1010 organisms of an 0127:H6 Hep-2-adhesive class I strain (E2348/69) or its plasmid-minus, nonadhesive derivative. Diarrhea occurred in nine of 10 volunteers who ingested the parent strain (mean, 1,178 ml) but in only two of nine who took the plasmid-minus variant (mean, 433 ml; P < .006). All volunteers ill from strain E2348/69 mounted serum IgA and IgG responses to a 94-kDa plasmid-associated outer membrane protein of E2348/69; this protein was found in other class I EPEC but not in enterotoxigenic or meningitic strains. The 50-70-MDa EAF plasmid seems neces- sary for full expression of pathogenicity in EPEC that exhibit Hep-2 adhesiveness. EPEC isolates of certain other, less common, 0 serogroups (044, 086, and 0114) are rarely Hep-2 adhesive. These EPEC, designated class II, possess distinct 50-70 MDa plasmids lacking EAF genes. Diarrhea was caused by 108 or 1010 organisms of an 0114:H2 class II EPEC strain (mean, 1,156 ml) in six of 11 volunteers. This result confirmed that class II EPEC are pathogenic by a mechanism not involving Hep-2 adhesiveness