Virulence Strategies Of LEE-negative Shiga Toxigenic Escherichia Coli
Funder
National Health and Medical Research Council
Funding Amount
$230,246.00
Summary
Shiga toxigenic Escherichia coli (STEC) are a diverse group of pathogens that cause serious gastrointestinal disease in humans, which can lead to life-threatening complications. This project is aimed at understanding how these bacteria cause disease, and is focused on a subset of STEC strains that are highly virulent and produce a novel cytotoxin. A better understanding of the pathogenic mechanisms of STEC is essential for development of improved therapeutic and preventative strategies.
Pathogenesis And Prevention Of Shiga Toxigenic Escherichia Coli Infections
Funder
National Health and Medical Research Council
Funding Amount
$341,320.00
Summary
Shiga toxin (Stx)-producing strains of Escherichia coli (STEC) are known to cause diarrhoea and haemorrhagic colitis in humans. In a proportion of cases, this leads to potentially fatal systemic complications, such as haemolytic uraemic syndrome (HUS), which is the commonest cause of acute renal failure in children. HUS has a high mortality rate in spite of intensive supportive therapy. Morbidity is also substantial, as permanent renal damage and neurological sequelae occur in a significant prop ....Shiga toxin (Stx)-producing strains of Escherichia coli (STEC) are known to cause diarrhoea and haemorrhagic colitis in humans. In a proportion of cases, this leads to potentially fatal systemic complications, such as haemolytic uraemic syndrome (HUS), which is the commonest cause of acute renal failure in children. HUS has a high mortality rate in spite of intensive supportive therapy. Morbidity is also substantial, as permanent renal damage and neurological sequelae occur in a significant proportion of survivors. Large outbreaks of STEC infection are becoming increasingly common, and highlight the threat to public health posed by these bacteria. The serious systemic complications of STEC disease, as well as much of the intestinal pathology, are directly attributable to Stx. However, pathogenesis is multifactorial and capacity of the bacteria to colonize the gut is a crucial virulence trait. STEC infections can now be diagnosed very early in the course of disease, but currently no effective therapeutic intervention is possible. We are addressing this deficiency by developing a novel therapy for STEC infections based on a genetically modified harmless bacterium capable of binding toxin in the gut. Vaccines capable of preventing transmission of STEC disease in the community are also needed, but development of these demands a full understanding of the mechanisms whereby diverse STEC strains adhere to intestinal epithelium and colonize the human gut. We are therefore also examining the interaction between STEC and gut epithelial cells at the cellular and molecular level, with a view to identifying and assessing the vaccine potential of key determinants of adherence.Read moreRead less
Dissemination And Virulence Properties Of The She Pathogenicity Island Of Shigella Flexneri.
Funder
National Health and Medical Research Council
Funding Amount
$110,625.00
Summary
Bacterial species belonging to the genus Shigella are responsible for intestinal diseases ranging from mild diarrhoea to life threatening bacillary dysentery. Such diseases kill over a million people, mainly infants in developing countries, every year and lead to serious morbidity and mortality even in industrialised countries with well developed health care systems. In many cases the virulence of Shigella species is augmented by large fragments of DNA, called pathogenicity islands, that carry g ....Bacterial species belonging to the genus Shigella are responsible for intestinal diseases ranging from mild diarrhoea to life threatening bacillary dysentery. Such diseases kill over a million people, mainly infants in developing countries, every year and lead to serious morbidity and mortality even in industrialised countries with well developed health care systems. In many cases the virulence of Shigella species is augmented by large fragments of DNA, called pathogenicity islands, that carry genes which contribute to the development of disease (pathogenesis) in humans. Pathogenicity islands are important genetic elements which appear to spread independantly throughout bacterial populations and therefore contribute to the emergence of new virulence traits in bacteria. Recently, we identified two related pathogenicity islands carried by both Shigella flexneri and other species of the genus Shigella. The two pathogenicity islands belong to a unique class of genetic elements found in Shigella species and virulent strains of the intestinal bacterium E. coli. Our current study is aimed at (1) understanding the mechanisms by which one of these islands, the she pathogenicity island, spreads from one bacterial strain to another to introduce disease-producing or virulence genes to new bacteria and (2) to study how the sigA virulence gene, carried on the she pathogenicity island, contributes to disease development in humans. We know that sigA encodes a protein toxin which contributes to the loss of fluid from the intestines of rabbits that have been experimentally infected with Shigella flexneri. We propose to study the structure and function of the SigA protein to determine how it interacts with tissues to produce a pathological state. Such studies will enhance our understanding of the process of disease development and contribute to the investigation and assessment of new strategies for therapeutic intervention.Read moreRead less
Contribution Of Shigella And Escherichia Coli Pathogenicity Islands To Diarrhoeal Disease
Funder
National Health and Medical Research Council
Funding Amount
$303,677.00
Summary
Diarrhoea resulting from infection with Shigella and Escherichia coli is a major cause of sickness and death in the developing world, especially in children. Even in Australia, these bacteria, which may be food borne, are occasionally responsible for life threatening infections. In this study, we will investigate the contribution to diarrhoeal disease of large fragments of foreign DNA which have been recently acquired by these bacteria. We will characterise several of these elements in detail, i ....Diarrhoea resulting from infection with Shigella and Escherichia coli is a major cause of sickness and death in the developing world, especially in children. Even in Australia, these bacteria, which may be food borne, are occasionally responsible for life threatening infections. In this study, we will investigate the contribution to diarrhoeal disease of large fragments of foreign DNA which have been recently acquired by these bacteria. We will characterise several of these elements in detail, identifying novel virulence determinants and toxins in the process. We will also explore the means by which these packages of nasty DNA transfer between bacteria and investigate their potential to give rise to new, more virulent strains of bacteria. This study is particularly significant because it will lead to an improved understanding of how bacteria cause disease and may help to guide us in developing better strategies for the prevention of bacterial diarrhoea. Specifically, the work done on characterising large clusters of virulence genes will allow us to construct safer bacterial vaccines and we expect that in the future this knowledge will contribute to the development of new and better diagnostic and therapeutic agents against these harmful bacteria.Read moreRead less
Origins And Relationships Of Shigella And Enteroinvasive Escherichia Coli
Funder
National Health and Medical Research Council
Funding Amount
$377,310.00
Summary
Shigella is a well known highly infectious human pathogen with as few as 10 cells allowing effective spread by infected food or water, and also by person to person contact. Shigellosis is a particularly significant disease for children due to lack of pre-existing immunity and greater chance of transfer by fecal-oral route. One group of E. coli called Enteroinvasive E. coli (EIEC) resembles Shigella in many aspects from disease symptoms to biochemical properties. EIEC is a major cause of diarrhoe ....Shigella is a well known highly infectious human pathogen with as few as 10 cells allowing effective spread by infected food or water, and also by person to person contact. Shigellosis is a particularly significant disease for children due to lack of pre-existing immunity and greater chance of transfer by fecal-oral route. One group of E. coli called Enteroinvasive E. coli (EIEC) resembles Shigella in many aspects from disease symptoms to biochemical properties. EIEC is a major cause of diarrhoea in less developed countries and has also caused large outbreaks in developed countries. It is now clear that Shigella and E. coli are really one species. EIEC and Shigella strains are variants of E. coli with humans as the only host. However separation of the two in all records and most studies means that there is no integrated understanding of the forms. We aim to study the relationships of Shigella and EIEC and expect significant insights into the origins of Shigella-EIEC. This will facilitate diagnosis and understanding of the disease(s) and lead to a far better classification . EIEC-Shigella strains have arisen from other E. coli independently. This has happened seven times in the derivation of Shigella and we expect more such events with EIEC. An interesting phenomenon during this process is that strains tend to lose metabolic functions. In this study we will look at what, why and how functions are lost. O antigens are important in evading the host immune system. Shigella strains obtained many O antigens, the majority apparently from other species. This is quite likely the key to its success. We will look at how Shigella obtained new O antigens. This project will be significant in the understanding of Shigell-EIEC, a very significant human pathogen, and in general for understanding emergence of new pathogens.Read moreRead less
Examination Of The Role Of Biofilms In Infection With Enteropathogenic Escherichia Coli
Funder
National Health and Medical Research Council
Funding Amount
$456,382.00
Summary
Many infections are caused by bacteria living in communities, known as biofilms. Enteropathogenic E. coli (EPEC) is a major cause of diarrhoea and results in the death of millions of children annually. We have found a link between biofilm formation by EPEC and disease. In this project we will examine how biofilm formation by EPEC occurs and the contribution of biofilm formation to disease. The results of this study may indicate new ways to treat and prevent E. coli diarrhoea.
Identification And Characterisation Of Novel Virulence Genes In Attaching And Effacing Strains Of Escherichia Coli
Funder
National Health and Medical Research Council
Funding Amount
$281,320.00
Summary
Some varieties of Escherichia (E.) coli are harmless bacteria that live in the healthy intestinal tract, whereas others can cause diarrhoea. Those varieties of E. coli which cause diarrhoea include so-called enteropathogenic E. coli (EPEC), which is a leading cause of life- diarrhoea in infants and young children in less developed countries, and enterohaemorrhagic E. coli (EHEC) the cause of hamburger disease. These bacteria are able to cause disease because they possess specific genetic informa ....Some varieties of Escherichia (E.) coli are harmless bacteria that live in the healthy intestinal tract, whereas others can cause diarrhoea. Those varieties of E. coli which cause diarrhoea include so-called enteropathogenic E. coli (EPEC), which is a leading cause of life- diarrhoea in infants and young children in less developed countries, and enterohaemorrhagic E. coli (EHEC) the cause of hamburger disease. These bacteria are able to cause disease because they possess specific genetic information that is absent from harmless varieties of E. coli. Although many of these disease-associated genes have been identified, the specific role of many of them is not known. In addition, it seems likely that many more genes of this type remain to be discovered. The fact that EPEC is host specific means that the mechanisms by which these bacteria cause disease can only be investigated in humans. This is extremely limiting for the number and type of investigations that can be performed. However, there are rabbit-specific strains of EPEC which cause a disease in rabbits that is indistinguishable from that caused by EPEC in children. The aims of this study are to use the rabbit model of diarrhoea to learn more about the contribution of certain specific factors of EPEC to disease causation and to discover new factors of this type. This will be achieved by three complementary strategies: (1) investigating rabbit E. coli for virulence genes and determining if they are present in human strains; (2) examining the effect of inactivating these genes on the ability of E. coli to cause diarrhoea in rabbits; and (3) infecting rabbits with pools of mutant E. coli strains to identify factors that the bacteria require to survive in rabbits. The results of these studies will improve understanding of the mechanisms by which E. coli cause disease and may provide opportunities for the development of novel tools to diagnose, treat and prevent E. coli-associated diarrhoea.Read moreRead less
Evolution And Function Of A Novel Lateral Flagellar Locus, Flag-2, In Pathogenic Escherichia Coli
Funder
National Health and Medical Research Council
Funding Amount
$465,158.00
Summary
This project will study how the bacteria that cause infant diarrhoea colonize the intestine and induce disease. We have identified a novel genetic region that allows E. coli to survive and persist in the intestine. Similar genes are also present in closely related organisms. This project will help us to undestand how new diseases evolve and emerge and may lead to the development of new vaccines to protect against infant diarrhoea.
Shigella Flexneri O Antigen Polysaccharides: Biosynthesis, Function In Virulence, And Interaction With IcsA/VirG
Funder
National Health and Medical Research Council
Funding Amount
$468,055.00
Summary
Shigella flexneri bacteria cause dysentery in millions of humans each year. The bacterium invades and replicates within the cells of the large intestine. Inside cells, S. flexneri is able to use the host cell's actin-based motility machinery to become motile within the cells, and this can be seen as F-actin comet tails extending from one end of the cell. Bacterial cell surface components residing in the outer membrane are important for the bacterium's ability to cause disease. Two of these compo ....Shigella flexneri bacteria cause dysentery in millions of humans each year. The bacterium invades and replicates within the cells of the large intestine. Inside cells, S. flexneri is able to use the host cell's actin-based motility machinery to become motile within the cells, and this can be seen as F-actin comet tails extending from one end of the cell. Bacterial cell surface components residing in the outer membrane are important for the bacterium's ability to cause disease. Two of these components (lipopolysaccharides (LPS) and their polysaccharide chains (O antigens), and IcsA-VirG protein)) are required for initiating actin polymerisation, and mutations affecting synthesis of these components reduce ability to cause disease. In previous studies we have found that O antigen and the synthesis and function of IcsA are interrelated. This project will study how the O antigens are synthesised and their chain length determined by the Wzz protein, and the Wzz structure in relation to its function will also be characterised. The role played by O antigen in intracellular motility will be studied to determine the mechanisms involved. Infection of cells and cell free extracts, antibodies, and an enzyme which specifically degrades the O antigen, will be used to study how O antigen affect the interaction between bacteria with human cell proteins. The relationship between O antigen and IcsA function will be studied using monoclonal antibodies raised to IcsA. The effect of LPS on the outer membrane protease IcsP will be investigated, as will the effect of LPS lipid A mutations on O antigen and virulence. These studies will contribute to a better understanding of the biosynthesis of an ubiquitous bacterial cell surface component (O antigen), its function as a virulence factor in bacterial interactions with host cells. This may lead to novel therapeutic strategies to prevent and control Shigellosis and other bacterial infections.Read moreRead less
Pathogenesis Of Infections With Yersinia Enterocolitica
Funder
National Health and Medical Research Council
Funding Amount
$339,634.00
Summary
Yersinia enterocolitica is a significant cause of food-poisoning, gastroenteritis and abdominal pain which may be mistaken for acute appendicitis. Y. enterocolitica is a heterogenous bacterial species only some strains of which are able to cause disease. Many of the disease-causing strains have readily identifiable virulence determinants which facilitate their detection in clinical microbiological laboratories. By contrast, other types, in particular the biotype 1A strains, lack these determinan ....Yersinia enterocolitica is a significant cause of food-poisoning, gastroenteritis and abdominal pain which may be mistaken for acute appendicitis. Y. enterocolitica is a heterogenous bacterial species only some strains of which are able to cause disease. Many of the disease-causing strains have readily identifiable virulence determinants which facilitate their detection in clinical microbiological laboratories. By contrast, other types, in particular the biotype 1A strains, lack these determinants, although many of them are significantly associated with disease. During the past few years, we have compared biotype 1A strains of Y. enterocolitica obtained from patients with those from non-clinical sources in a number of assays for virulence-associated properties. These studies have shown that clinical isolates differ from non-clinical ones in terms of their ability to (1) invade epithelial cells in vitro and intestinal absorptive cells in vivo, (2) escape from epithelial cells and macrophages they have invaded, (3) resist killing by macrophages, and (4) colonise the intestinal tracts of mice. The aim of the study is to identify the bacterial determinants responsible for these differences between clinical and non-clinical strains of Y. enterocolitica biotype 1A. This will be achieved by using genetic techniques to modify virulent strains of biotype 1A at random and then identify derivatives of these bacteria with altered virulence properties. We shall also use genetic techniques to identify genes that are specifically activated when the bacteria come into contact with animal cells and tissues. The results of this research will provide new insights into the virulence mechanisms of Y. enterocolitica and related bacteria, and will be used to develop diagnostic tests which will allow pathogenic strains to be distinguished from harmless ones.Read moreRead less