title: Interrogation of single nucleotide polymorphisms in gnd provides a novel method for molecular serogrouping of clinically important Shiga toxin producing Escherichia coli (STEC) targeted by regulation in the United States, including the "big six" non-O157 STEC and STEC O157.
abstract: Escherichia coli O157:H7 has frequently been associated with foodborne infections and is considered an adulterant in raw non-intact beef in the U.S. Shiga toxin-producing E. coli (STEC) belonging to serogroups O26, O45, O103, O111, O121, and O145 (known as the "big six" non-O157) were estimated to cause >70% of foodborne infections attributed to non-O157 serogroups in the U.S., as a result, these six serogroups have also been targeted by regulation in the U.S. The purpose of this study was to develop a rapid and high-throughput molecular method to group STEC isolates into seven clinically important serogroups (i.e., O157 and the "big six" non-O157 serogroups) targeted by regulation in the U.S. by interrogating single nucleotide polymorphisms (SNPs) in gnd. A collection of 195 STEC isolates, including isolates belonging to O157:H7 (n=18), O26 (n=21), O45 (n=19), O103 (n=24), O111 (n=24), O121 (n=23), O145 (n=21), and ten other STEC serogroups (n=45), was assembled and characterized by full gnd sequencing to identify informative SNPs for molecular serogrouping. A multiplex SNP typing assay was developed to interrogate twelve informative gnd SNPs by single base pair extension chemistry and used to characterize the STEC isolate collection assembled here. SNP types were assigned to each isolate by the assay and polymorphisms were confirmed with gnd sequence data. O-serogroup-specific SNP types were identified for each of the seven clinically important STEC serogroups, which allowed the differentiation of these seven STEC serogroups from other non-O157 STEC serogroups. Although serogroups of the "big six" non-O157 STEC and O157:H7 contained multiple SNP types per O-serogroup, there were no overlapping SNP types between serogroups. Our results demonstrate that molecular serogrouping of STEC isolates by interrogation of informative SNPs in gnd represents an alternative to traditional serogrouping by agglutination for rapid and high-throughput identification of clinically important STEC serogroups targeted by regulation for surveillance and epidemiological investigations.
authors.affiliation: Department of Food and Animal Sciences, Texas Tech University, Lubbock, TX 79409, United States; Department of Animal Sciences, Colorado State University, Fort Collins, CO 80523, United States.
authors.forename: J R
authors.initials: JR
authors.lastname: Elder
authors.affiliation: Department of Food and Animal Sciences, Texas Tech University, Lubbock, TX 79409, United States.
authors.forename: M
authors.initials: M
authors.lastname: Bugarel
authors.affiliation: Department of Food and Animal Sciences, Texas Tech University, Lubbock, TX 79409, United States; Department of Food Science and Technology, Cornell University, Ithaca, NY 14853, United States.
authors.forename: H C
authors.initials: HC
authors.lastname: den Bakker
authors.affiliation: Department of Food and Animal Sciences, Texas Tech University, Lubbock, TX 79409, United States.
authors.forename: G H
authors.initials: GH
authors.lastname: Loneragan
authors.affiliation: Department of Food and Animal Sciences, Texas Tech University, Lubbock, TX 79409, United States; Department of Animal Sciences, Colorado State University, Fort Collins, CO 80523, United States. Electronic address: kendra.nightingale@ttu.edu.
authors.forename: K K
authors.initials: KK
authors.lastname: Nightingale
mesh_terms: D000818:Animals; D004927:Escherichia coli Infections / Q000382:microbiology; D019453:Escherichia coli O157 / Q000235:genetics / Q000276:immunology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000276:immunology; D005243:Feces / Q000382:microbiology; D005838:Genotype; D057166:High-Throughput Screening Assays; D006801:Humans; D008460:Meat / Q000382:microbiology; D058889:Molecular Typing / Q000379:methods*; D019081:O Antigens / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D065288:Serogroup; D012703:Serotyping / Q000379:methods*; D054323:Shiga-Toxigenic Escherichia coli / Q000145:classification* / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D014481:United States
chemical_list: D029968:Escherichia coli Proteins; D019081:O Antigens
keywords: E. coli O157:H7; Molecular serotyping; Non-O157 STEC; SNP typing; Shiga toxin producing Escherichia coli (STEC); gnd