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The Diarrheal Response Of Humans To Some Classic Serotypes Of Enteropathogenic Escherichia Coli Is Dependent On A Plasmid Encoding An Enteroadhesiveness Factor, Myron M. Lavine, James P. Nataro, Helge Karch, Mary M. Baldini, James B. Kaper, Robert E. Black, Mary Lou Clements, Alison D. O'Brien

Uniformed Services University of the Health Sciences

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 …