Identification of Putative Virulence Biomarkers in Pathogenic Shiga Toxin-Producing Escherichia coli
Open Access
- Author:
- McIntyre, Emily Abbie
- Area of Honors:
- Food Science
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Edward G Dudley, Thesis Supervisor
Stephen John Knabel, Thesis Honors Advisor - Keywords:
- Virulence
Pathogenic
Shiga toxin-producing Escherichia coli
STEC
Enterohemorrhagic Escherichia coli
EHEC
Escherichia coli
foodborne pathogens - Abstract:
- Shiga toxin-producing E. coli (STEC) are zoonotic pathogens that produce Shiga toxins, causing illness in humans ranging from mild diarrhea to bloody diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. Enterohemorrhagic E. coli (EHEC), such as E. coli O157:H7, are a subset of STEC that are capable of causing the most severe disease, such as hemorrhagic colitis and the hemolytic uremic syndrome, in humans. E. coli O157:H7 is the STEC most frequently isolated from clinical outbreaks, with raw ground beef being the most common vehicle for transmission. While the unique biochemical properties of E. coli O157:H7 have made detecting this serotype fairly straightforward, other STEC that are capable of causing disease lack distinguishing biochemical characteristics and have been underrecognized as pathogens. The increased recognition of non-O157 STEC as a cause of disease and outbreaks has made detecting them in food and in clinical samples of great importance. Also, because not all STEC are capable of causing disease, there is need for a method of differentiating highly virulent from less harmful strains. A recent study identified 87 genes that are conserved among fully sequenced strains of O157, O26, O111, and O103 serogroups but absent in other E. coli. The objective of this study was to determine if these 87 genes are present in a larger collection of EHEC strains and to determine the prevalence of a subset of these genes in STEC. The nleB gene, encoded on OI-122 (a genome segment found in E. coli O157:H7 but not E. coli K-12), is an effector gene of the type III secretion system. This gene was found in all isolates of O26, O103, O111, O157, O145, and O121, but was less prevalent in other STEC serogroups. The results of this study indicate that nleB is the most reliable marker of virulence among the STEC isolates screened.