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United States Department of Agriculture

Agricultural Research Service

Research Project: EXPLORING GENOMIC DIFFERENCES AND ECOLOGICAL RESERVOIRS TO CONTROL FOODBORNE PATHOGENS

Location: Meat Safety & Quality Research

Title: Association of nucleotide polymorphisms within the O-antigen gene cluster of Escherichia coli O26, O45, O103, O111, O121, and O145 with serogroups and genetic subtypes

Authors
item Norman, Keri
item Strockbine, Nancy -
item Bono, James

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 6, 2012
Publication Date: September 1, 2012
Citation: Norman, K.N., Strockbine, N.A., Bono, J.L. 2012. Association of nucleotide polymorphisms within the O-antigen gene cluster of Escherichia coli O26, O45, O103, O111, O121, and O145 with serogroups and genetic subtypes. Applied and Environmental Microbiology. 78(18):6689-6703.

Interpretive Summary: Recent studies have found non-O157 Shiga toxin-encoding Escherichia coli (STEC) to be important contributors to human illness. One of the primary challenges in studying non-O157 STEC is the lack of standardized testing procedures. The purpose of this study was to identify genomic targets in E. coli serogroups O26, O45, O103, O111, O121, and O145 that differentiate strains that contain Shiga toxin-encoding genes from those that do not. From genomic sequencing, we identified at least one target in each of the serogroups that differentiated between STEC and non-STEC strains. The targets identified in this study can be used to design tests to screen for STEC non-O157 E. coli in the six O-serogroups. The ability to differentiate between STEC and non-STEC strains will be important for regulatory agencies and the meat industry when testing for serogroups O26, O45, O103, O111, O121, and O145.

Technical Abstract: Shiga toxin-producing Escherichia coli (STEC) cause severe disease and hemorrhagic colitis in humans. Of the STECs, E. coli O157:H7 is the most widely recognized and researched serotype, and the majority of cases of hemolytic-uremic syndrome in the United States are associated with this serotype. However, focus has recently shifted to STEC non-O157 serogroups and a study conducted by the Centers for Disease Control and Prevention found that serogroups O26, O45, O103, O111, O121, and O145 were also responsible for cases of severe disease. The purpose of this study was to identify single nucleotide polymorphisms (SNPs) in the O-antigen operon that are specific to E. coli serogroups O26, O45, O103, O111, O121, and O145 and differentiate between STEC and non-STEC strains. Genetic sequencing of the O-antigen operon was used to identify SNPs in 164 strains and virulence gene profiles were compared between and among serogroups. MALDI-TOF assays were designed to validate the accuracy of the SNPs identified through genetic sequencing. We found at least one SNP that was specific to each O-serogroup and also differentiated between STEC and non-STEC strains with a high specificity and sensitivity. Differences in the genetic sequence of the O-antigen operon corresponded well with differences in the virulence gene profiles and provided evidence of different lineages for STEC and non-STEC strains. The SNPs discovered in this study can be used to develop tests that will not only accurately identify O26, O45, O103, O111, O121, and O145 strains but also strains that contain Shiga toxin-encoding genes.

Last Modified: 4/25/2014
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