EVALUATION OF THE PREMIER EHEC ASSAY FOR DETECTION OF SHIGA TOXIN-PRODUCING ESCHERICHIA-COLI

An enzyme-linked immunosorbent assay for the detection of Shiga toxins (Premier EHEC assay; Meridian Diagnostics, Inc.) was compared to conv entional sorbitol-MacConkey culture for the recovery of enterohemorrha gic Escherichia coli, A total of 74 enteric pathogens, including 8 E. coli O157:H7 isolates, were recovered from 974 stool specimens, Two of these specimens were not tested by Premier assaying due to insufficie nt sample and are not considered in the data analysis, The Premier EHE C assay detected the 6 evaluable specimens which were culture positive for B. coli O157:H7 and identified an additional 10 specimens as cont aining Shiga toxin, Seven isolates were recovered from these 10 specim ens by an immunoblot assay and were confirmed as toxin producers by a cytotoxin assay, Of these seven, four isolates were serotype O157:H7, one was O26:NM, one was O6:H-, and one was O untypeable:a untypeable. Three specimens contained Shiga toxin by both EHEC immunoassaying and cytotoxin testing; however, no cytotoxin-producing E. coli could be re covered, The sorbitol-MacConkey method had a sensitivity and a specifi city of 60 and 100%, respectively, while the Premier EHEC assay had a sensitivity and a specificity of 100 and 99.7%, respectively, for E. c oli O157:H7 only, The Premier EHEC assay also detected an additional 2 0% Shiga toxin-producing E. coli (STEC) that were non-O157:H7. Thus, t he Premier EHEC assay is a sensitive and specific method for the detec tion of all STEC isolates, Routine use would improve the detection of E. coli O157:H7 and allow for determination of the true incidence of S TEC other than O157:H7, The presence of blood in the stool and/or the ages of the patients were poor predictors of the presence of STEC, Cri teria need to be determined which would allow for the cost-effective i ncorporation of this assay into the routine screen for enteric pathoge ns in high-risk individuals, especially children.