title: Latex agglutination assays for detection of non-O157 Shiga toxin-producing Escherichia coli serogroups O26, O45, O103, O111, O121, and O145.
abstract: Latex agglutination assays utilizing polyclonal antibodies were developed for the top six non-O157 Shiga toxin-producing Escherichia coli (STEC) serogroups. Rabbit antisera were affinity purified through protein A/G columns, and the isolated immunoglobulins (IgGs) were  covalently immobilized onto polystyrene latex particles. The resulting latex-IgG complex had a protein (IgG) load of 0.20 to 0.28 mg/ml in a 1% latex suspension. Optimum conditions for the agglutination assay consisted of utilizing 20 μm l of latex-IgG reagent containing 2.0 to 2.8 μm  g IgG in a 0.5% latex suspension. Agglutination or flocculation was observed almost instantly after mixing the colonies with the latex-IgG, indicating STEC strains. More than 100 target and nontarget strains were tested in more than 3,000 test replicates. All target organisms produced positive  results, but three antisera (anti-O26, anti-O103, and anti-O145) cross-reacted with some other STECs. The anti-O103 and anti-O145 latex reagents cross-reacted with O26 strains, and the anti-O26 cross-reacted with O103 strains. The latex-IgG reagents are stable for at least 1 year and are easy  to prepare. These agglutination assays can be used for identification of presumptive non-O157 STEC colonies from agar media. The techniques used to prepare the latex reagents also can be utilized for testing other STEC serogroups, other E. coli serotypes, or other pathogens to ensure  safe foods to consumers.
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, Wyndmoor, PA 19038, USA. marjorie.medina@ars.usda.gov
authors.forename: Marjorie B
authors.initials: MB
authors.lastname: Medina
authors.forename: Weilin L
authors.initials: WL
authors.lastname: Shelver
authors.forename: Pina M
authors.initials: PM
authors.lastname: Fratamico
authors.forename: Laurie
authors.initials: L
authors.lastname: Fortis
authors.forename: Glenn
authors.initials: G
authors.lastname: Tillman
authors.forename: Neelam
authors.initials: N
authors.lastname: Narang
authors.forename: William C
authors.initials: WC
authors.lastname: Cray
authors.forename: Emilio
authors.initials: E
authors.lastname: Esteban
authors.forename: Andchitrita
authors.initials: A
authors.lastname: Debroy
mesh_terms: D000818:Animals; D003257:Consumer Product Safety; D019453:Escherichia coli O157 / Q000145:classification* / Q000302:isolation & purification*; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D007841:Latex Fixation Tests / Q000379:methods*; D011817:Rabbits; D012703:Serotyping
chemical_list: D007074:Immunoglobulin G