Molecular analysis of regulation of virulence gene expression in pathogenic E. coli strains (ETEC and atypical EPEC)

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Infectious diarrhoea is one of the commonest human afflictions worldwide, and is responsible for the deaths of millions of children each year. One of the principal causes of diarrhoea is pathogenic E. coli, which are classified into several groups according to the factors they employ to cause disease. One type of pathogenic E. coli, known as enterotoxigenic E. coli (ETEC), causes diarrhoea resembling cholera in children in less developed countries and in adult travellers to those countries. Another type is enteropathogenic E. coli (EPEC), which causes acute and persistent diarrhoea in children worldwide. Recent studies in Melbourne and Darwin have shown that EPEC are a particularly common cause of diarrhoea in children living in those cities. Individual groups of E. coli use different strategies to cause infection. In the case of ETEC, the key step in infection is the injection of bacterial toxins into intestinal cells. These toxins perturb the ability of these cells to transport water and electrolytes across their membrane. In contrast, infection with EPEC is characterised by intimate adherence of the bacteria to the lining of the intestine, causing structural damage to intestinal cells. Because the synthesis of virulence factors is an energy-costly process for bacteria, pathogenic varieties of E. coli have evolved sophisticated mechanisms to control the production of these factors, so that they are made only when needed, e.g., under environmental conditions like those in the gut. In this project, we will investigate the ways by which ETEC and EPEC sense and respond to environmental signals to produce their virulence determinants. The identification of specific control genes and proteins of these bacteria may lead to the development of novel diagnostic tools for EPEC and help us to devise new treatment strategies to block the production of virulence factors by pathogenic E. coli.