title: A polyclonal antibody based immunoassay detects seven subtypes of Shiga toxin 2 produced by Escherichia coli in human and environmental samples.
abstract: BACKGROUND
  Shiga toxin-producing Escherichia coli (STEC) are frequent causes of severe human diseases ranging from diarrhea to hemolytic uremic syndrome. The existing strategy for detection of STEC relies on the unique sorbitol-negative fermentation property of the O157 strains, the most commonly identified serotype has been E. coli O157. It is becoming increasingly evident, however, that numerous non-O157 STEC serotypes also cause outbreaks and severe illnesses. It is necessary to have new methods that are capable of detecting all STEC strains.
  
  
  RESULTS
  Here we describe the development of a sandwich ELISA assay for detecting both O157 and non-O157 STECs by incorporating a novel polyclonal antibody (pAb) against Stx2. The newly established immunoassay was capable of detecting Stx2a spiked in environmental samples with a limit of detection between 10 and 100 pg/mL in soil and between 100 and 500 pg/mL in feces. When applied to 36 bacterial strains isolated from human and environmental samples, this assay detected Stx2 in all strains that were confirmed to be stx2-positive by real-time PCR, demonstrating a 100% sensitivity and specificity.
  
  
  CONCLUSIONS
  The sandwich ELISA developed in this study will enable any competent laboratory to identify and characterize Stx2-producing O157 and non-O157 strains in human and environmental samples, resulting in rapid diagnosis and patient care. The results of epitope mapping from this study will be useful for further development of a peptide-based antibody and vaccine.
authors.affiliation: Western Regional Research Center, Agricultural Research Service, United States Department of Agriculture (USDA), Albany, California, United States of America.
authors.forename: Xiaohua
authors.initials: X
authors.lastname: He
authors.forename: Stephanie
authors.initials: S
authors.lastname: Patfield
authors.forename: Robert
authors.initials: R
authors.lastname: Hnasko
authors.forename: Reuven
authors.initials: R
authors.lastname: Rasooly
authors.forename: Robert E
authors.initials: RE
authors.lastname: Mandrell
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology*; D000918:Antibody Specificity / Q000276:immunology; D000942:Antigens, Bacterial / Q000276:immunology; D002522:Chlorocebus aethiops; D004783:Environmental Microbiology; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D006801:Humans; D007106:Immune Sera / Q000276:immunology; D007114:Immunization; D007118:Immunoassay / Q000379:methods*; D007074:Immunoglobulin G / Q000276:immunology; D009500:Neutralization Tests; D022641:Shiga Toxin 2 / Q000096:biosynthesis* / Q000145:classification* / Q000276:immunology / Q000302:isolation & purification; D054323:Shiga-Toxigenic Escherichia coli / Q000276:immunology*; D014709:Vero Cells; D014871:Water Microbiology
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D007106:Immune Sera; D007074:Immunoglobulin G; D022641:Shiga Toxin 2