Evaluation of ELISA tests specific for Shiga toxin 1 and 2 in food and water samples

Authors: Gehring, Andrew; Fratamico, Pina; Lee, Joseph - Joe; RUTH, LEAH - Abraxis, Llc; He, Xiaohua; He, Yiping; Paoli, George; Stanker, Larry; RUBIO, FERNANDO - Abraxis, Llc

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2017
Publication Date: 2/3/2017
Publication URL: https://handle.nal.usda.gov/10113/5651962
Citation: Gehring, A.G., Fratamico, P.M., Lee, J., Ruth, L., He, X., He, Y., Paoli, G., Stanker, L.H., Rubio, F.M. 2017. Evaluation of ELISA tests specific for Shiga toxin 1 and 2 in food and water samples. Food Control. 77:145-149.

Interpretive Summary: Most E. coli bacteria are benign, however, the harmful enterohemorrhagic E. coli may cause kidney failure, brain damage, or even death. This E. coli is different from benign E. coli since it contains genes for either one or both toxins, Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2). In collaboration with ARS researchers, a diagnostic kit-producing company developed and generated a new assay kit that, unlike other similar rapid test products, has the ability to distinguish E. coli bacteria that produce either Stx1 or Stx2. This is an important feature since Stx2 is approx. 400 times more lethal than Stx1. In addition, the ability to distinguish clinical or food (beef, Romaine lettuce, recreational water, and pasteurized milk were successfully tested) samples containing either toxin assists in efforts to identify the source of bacterial contamination. Food producers and regulators alike may use this assay to rapidly test for the presence of this toxin.

Technical Abstract: Two enzyme-linked immunosorbent assay (ELISA) kits were evaluated for their effectiveness in detecting and differentiating between Shiga toxin 1 and 2 (Stx1 and Stx2) produced by Shiga toxin-producing E. coli (STEC) inoculated into food and water samples. Each kit incorporated monoclonal antibodies previously determined to bind all known Stx1 or Stx2 subtypes with the exception of Stx2b. Four different sample types, including ground beef, Romaine lettuce, pond water, and pasteurized milk were inoculated with Stx1a-, Stx2a-, or Stx1a- and Stx2a-producing STEC strains, enriched using modified tryptic soy broth (containing mitomycin C) for 6, 16, and 22 h, and tested using the ELISA kits in the presence of a bacterial protein extraction reagent (B-PER TM). The two Shiga toxin types were readily detected and distinguished for all tested sample types. There was good overall sensitivity, specificity, variance, and reproducibility for the two ELISA kits and they should prove useful for application in food testing.