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Validation of Two New Immunoassays for Sensitive Detection of a Broad Range of Shiga Toxins

Q. Kong, S. Patfield, C. B Skinner, L. H. Stanker, A. G. Gehring, P. M. Fratamico, F. Rubio, W. Qi, X. He
Austin Immunology 2016 v.1 no.2 pp. 1007
Shiga toxin, agar, culture media, detection limit, diagnostic sensitivity, digestive system diseases, enterohemorrhagic Escherichia coli, enzyme-linked immunosorbent assay, fresh produce, humans, reproducibility, virulence
Shiga Toxin (Stx) is one of the major virulence factors produced by Shiga Toxin-producing E. coli (STEC) that cause severe human intestinal diseases. Although a few commercial assays for Stxs are available, they only detect a subset of Stxs. In this study, two new immunoassays, Abraxis Stx1 and Stx2, were evaluated and compared with the widely used Premier EHEC kit using the same set of standards developed in our laboratory. The new assays were demonstrated to be highly reliable and capable of detecting all 10 subtypes of Stxs and have a limit of detection for Stx1a and Stx2a down to 25 pg/mL, a 20-fold improvement over the Premier EHEC. When applied to forty-nine bacterial isolates collected from clinic, environmental and fresh produce samples, the new assays identified all but one stx2b-producing STEC strains, while the Premier EHEC ELISA missed two stx2e- and one stx2g-STEC stains. Furthermore, the new assays were also able to identify STEC strains using single colonies on agar plates without lengthy enrichment in liquid medium. The broad crossreactivity, robustness and high reproducibility and sensitivity of the new assays will be useful in reducing product recalls due to failures of detecting rare Stxs.