Humoral immune responses to Shiga-like toxins and Escherichia coli O157 lipopolysaccharide in hemolytic-uremic syndrome patients and healthy subjects

Shiga-like-toxin (SLT)-producing Escherichia coli strains, especially serotype O157:H7, are important causes of bloody diarrhea and are associated with the development of hemolytic-uremic syndrome (HUS). Enzyme-linked immunosorbent assays (ELISAs) were developed for the serologic detection of immunoglobulin M (IgM), IgG, and IgA to Shiga toxin (ST) and SLT-I, IgG to SLT-II, and IgM and IgG reactive against E. coli O157 lipopolysaccharide (LPS). Serum samples were collected from 27 HUS patients (25 pediatric and 2 adult) and tested in the ELISAs. Of 27 patients, 10 (37%) were positive for at least one class of antibody to ST/SLT-I. None of the patients were positive for IgG antibody to SLT-II. Twenty-one of the 27 patients (78%) were positive for antibody to E. coli O157 LPS; 19 of 27 (70%) were positive for IgM, and 20 of 27 (74%) were positive for IgG. None of 48 control serum samples were positive in any of the toxin assays, and only 1 of 48 (2%) and 2 of 48 (4%) were positive for IgM and IgG, respectively, to E. coli O157 LPS. Twelve of the 24 patients (50%) from whom stool specimens were collected were positive by culture for E. coli O157. Overall, serology and culture produced confirmation of infection by SLT-producing organisms in 23 of 27 (85%) HUS patients. A combination of ELISA for antibodies to E. coli O157 LPS and culture provided evidence for 22 of 27 (82%) of these patients. The results indicate that while ELISAs for ST/SLT-I and SLT-II antibodies were of limited diagnostic value, the ELISAs for IgM and IgG to E. coli O157 LPS provided valuable and sensitive adjuncts to culture.