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Title: Genotyping Escherichia coli O157:H7 for Its Ability to Cause Disease in Humans

item Bono, James - Jim

Submitted to: Current Protocols in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2009
Publication Date: 8/1/2009
Citation: Bono, J.L. 2009. Genotyping Escherichia coli O157:H7 for Its Ability to Cause Disease in Humans. Current Protocols in Microbiology. 14:5A.3.1-5A.3.10.

Interpretive Summary: An important factor in the ability of Escherichia coli O157:H7 to cause infection is its ability to adhere to epithelial cells. Proteins from two bacterial genes, tir and eae, are responsible for adherence to epithelial cells. Tir is injected by the bacteria into the epithelial cell where it integrates into the cell membrane and acts as a receptor for the eae gene product, a protein called intimin. DNA sequencing of these genes identified two variants that were able to distinguish between human and bovine sources. A real-time PCR assay was developed to rapidly identify E. coli O157:H7 isolates that belong to each group. This tool will provide researchers with a rapid and reliable method to characterize isolates and help improve our understanding of E. coli O157:H7 epidemiology and ecology.

Technical Abstract: Escherichia coli are ubiquitous in the world and for the most part are non-pathogenic and part of the normal lower gastrointestinal (GI) tract in mammals. However, there are pathogenic isolates that can cause severe disease that range from meningitis to hermorrhagic colitis (HC). In recent years, Shiga toxin-containing E. coli have been a major cause of food borne and environmental cases of HC and hemolytic uremic syndrome. The protocol developed will allow the use of polymerase chain reaction (PCR) for molecular serotyping of E. coli O157:H7 and identifying selected virulence factors. Traditional serotyping is carried out as an agglutination reaction using serotype-specific antibodies and is usually carried out at a reference laboratory. Molecular serotyping has several advantages over traditional serotyping. The information can be generated for less cost with faster turnaround time and further the method can serotype bacteria that are untypeable with the traditional method.