Regulation mechanisms of virulence genes in enterohemorrhagic Escherichia coli

Authors: GELALCHA, BENTI - University Of Tennessee; BROWN, SELINA - University Of Tennessee; CROCKER, HANNAH - University Of Tennessee; Agga, Getahun; KERRO DEGO, OUDESSA - University Of Tennessee

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2022
Publication Date: 8/3/2022
Citation: Gelalcha, B.D., Brown, S., Crocker, H., Agga, G.E., Kerro Dego, O. 2022. Regulation mechanisms of virulence genes in enterohemorrhagic Escherichia coli. Foodborne Pathogens and Disease. 19(9). https://doi.org/10.1089/fpd.2021.0103.
DOI: https://doi.org/10.1089/fpd.2021.0103

Interpretive Summary: Most strains of Escherichia coli bacteria reside in the intestinal tract of humans without causing illness. A few strains such as those causing hemorrhage in the human intestines and damage the kidneys cause life threatening infections. One of these strains is named enterohaemorrhagic E. coli (EHEC). These strains are the most common cause of food borne illnesses. Cattle are important reservoirs for most of the EHEC strains. As a result, the presence of top seven EHEC strains in ground beef and beef trimmings are declared as adulterants in the United States. People get infected mainly by consuming contaminated meat, vegetables, and water. The EHEC bacteria use two important tools to cause damage to infected people. These are their ability to attach themselves onto the surface of intestinal cells, and production of Shiga toxin. Their attachment and toxin production are regulated through a complex mechanism that involves several genes. They are triggered by bacterial, host and environmental factors. Thus, understanding the mechanism, and identification of the major proteins and environmental factors involved in the ability of the bacterial strains in causing diseases in humans and its regulation are important to develop control mechanisms.

Technical Abstract: Enterohemorrhagic Escherichia coli (EHEC) is one of the most common E. coli pathotypes reported to cause several outbreaks of foodborne illnesses. EHEC is a zoonotic pathogen, and ruminants, especially cattle, are considered important reservoirs for the most common EHEC serotype, E. coli O157:H7. Humans are infected indirectly through the consumption of food (milk, meat, leafy vegetables, and fruits) and water contaminated by animal feces or direct contact with carrier animals or humans. E. coli O157:H7 is one of the most frequently reported causes of foodborne illnesses in developed countries. It employs two essential virulence mechanisms to trigger damage to the host. These are the development of attaching and effacing (AE) phenotypes on the intestinal mucosa of the host and the production of Shiga toxin (Stx) that causes hemorrhagic colitis and hemolytic uremic syndrome. The AE phenotype is controlled by the pathogenicity island, the locus of enterocyte effacement (LEE). The induction of both AE and Stx is under strict and highly complex regulatory mechanisms. Thus, a good understanding of these mechanisms, major proteins expressed, and environmental cues involved in the regulation of the expression of the virulence genes is vital to finding a method to control the colonization of reservoir hosts, especially cattle, and disease development in humans. This review is a concise account of the current state of knowledge of virulence gene regulation in the LEE-positive EHEC.