Genetics And Biochemistry Of Biosynthesis Of The Cell Wall Of Mycobacteria
Funder
National Health and Medical Research Council
Funding Amount
$260,831.00
Summary
Mycobacteria commolnly cause human disease. The major killer in the group is Mycobacterium tuberculosis which annually causes millions of deaths from tuberculosis (TB) worldwide. Another pathogen from this group is Mycobacterium avium which often infects immunosuppressed people such as those with advanced HIV-AIDS. Mycobacteria have evolved a specialised wall that surrounds their cells which protects them from chemical attack from antibiotics and helps them to establish infections. The major ant ....Mycobacteria commolnly cause human disease. The major killer in the group is Mycobacterium tuberculosis which annually causes millions of deaths from tuberculosis (TB) worldwide. Another pathogen from this group is Mycobacterium avium which often infects immunosuppressed people such as those with advanced HIV-AIDS. Mycobacteria have evolved a specialised wall that surrounds their cells which protects them from chemical attack from antibiotics and helps them to establish infections. The major antibiotic used for TB stops cells from synthesising the protective layer thereby making them very vulnerable to human immune defences. Unfortunately, resistance to this antibiotic is common and new antibiotics are needed to treat mycobacterial infections. We are studying how mycobacteria make the cell wall and are looking for key steps where new drugs might be able to inhibit the process. Our approach is to inactivate genes in the mycobacteria that make the enzymes which control cell wall synthesis. The gene inactivation results in crippled mycobacteria that are unable to make proper cell walls. We analyse the cell wall changes that gene inactivation cause studying the chemical composition of the cell. This helps to identify the steps in cell wall biosynthesis and each step becomes a potential target for new drugs. Each of the weaken mycobacteria can be tested to see how well they can resist antibiotics and to see if they can survive host defences. In this way we can identify which components of the cell wall are critical for them to establish infections and resist antibiotic treatments. Enzymes that participate in the synthesis of such components are prime targets for us to concentrate on to design new antibiotics.Read moreRead less
Recombinant Bacteria Expressing Oligosaccharide Receptor Mimics For Prevention Of Enteric Infections
Funder
National Health and Medical Research Council
Funding Amount
$451,056.00
Summary
Gastrointestinal infectious diseases kill more than 3 million people each year. The principal microbial pathogens responsible for these infections are known to exploit oligosaccharides on the surface of host cells as receptors for ahesins or toxins. We have developed (and patented) a novel anti-infective strategy, based on mimicry of oligosaccharide receptors for toxins and adhesins produced by enteric pathogens on the surface of harmless carrier bacteria. Oral administration of such recombinant ....Gastrointestinal infectious diseases kill more than 3 million people each year. The principal microbial pathogens responsible for these infections are known to exploit oligosaccharides on the surface of host cells as receptors for ahesins or toxins. We have developed (and patented) a novel anti-infective strategy, based on mimicry of oligosaccharide receptors for toxins and adhesins produced by enteric pathogens on the surface of harmless carrier bacteria. Oral administration of such recombinant probiotics has the potential to prevent enteric infections by binding and neutralizing toxins in the gut lumen and by blocking adherence of the pathogen to intestinal epithelial cells. As a prototypic example, we have developed a bacterium capable of preventing the serious consequences of Shiga toxigenic Escherichia coli (STEC) infections; this agent binds Shiga toxin with very high efficiency and is 100% protective in animal models. The strategy has very broad applications, however, and receptors for virtually any pathogen can be mimicked by expression of appropriate glycosyl transferases in a suitable harmless host bacterium. This proposal involves extension of our existing work to develop therapeutic agents for other important life threatening diarrhoeal diseases including cholera, travellers' diarrhoea, dysentery, antibiotic-associated colitis, rotavirus, etc.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
Investigation Of The Association Between Chlamydial Infection And Asthma In Different Age Groups
Funder
National Health and Medical Research Council
Funding Amount
$382,117.00
Summary
Asthma is a common and severe lung disease that results from inflammation due to allergy and has symptoms of breathing difficulties, wheezing, chest tightness, and cough. Asthma is clinically characterised by the presence of certain types of responses from the immune system. We are looking for ways of preventing and curing asthma. There is a well known link between certain types of bacteria, called Chlamydia, and asthma but it is not known whether people develop asthma first and then get chlamyd ....Asthma is a common and severe lung disease that results from inflammation due to allergy and has symptoms of breathing difficulties, wheezing, chest tightness, and cough. Asthma is clinically characterised by the presence of certain types of responses from the immune system. We are looking for ways of preventing and curing asthma. There is a well known link between certain types of bacteria, called Chlamydia, and asthma but it is not known whether people develop asthma first and then get chlamydial infection or are infected first and this leads to asthma. We have shown that if adult mice are exposed to an allergen during chlamydial infection then the asthma gets worse. However, if newborn mice have a chlamydial infection then asthma is prevented when they are adults. These are preliminary observations, which we need to expand and understand the immune mechanisms that result in infection and allergy so that we can target them with antibiotics or vaccines. We will investigate how the timing of chlamydial infection relative to exposure to allergens (before, during or after) affects the development of asthma in adult mice. Newborns and young children have different immune systems to adults, so we will investigate what effects the infection of young mice has on infection and allergy later in life. We will also test a new vaccine we have developed against chlamydial infection to see if it can prevent chlamydial infection and infection-induced asthma. We will then examine if there is the same association between chlamydial infection and asthma in human asthmatics that present to hospital with exacerbation of their asthma. This work will help us develop new strategies for preventing and curing asthma, which may vary in different age groups. We will identify whether prevention of chlamydial infection by vaccination (or antibiotics) can be used to prevent and treat asthma.Read moreRead less
Environmental Regulation Of Virulence In Attaching And Effacing Enterobacteria
Funder
National Health and Medical Research Council
Funding Amount
$569,063.00
Summary
Disease-causing bacteria must respond to the extreme conditions, such as acid and bile, which they encounter in their hosts. They achieve this by sensing their environment and activating genes that enhance their survival and ability to cause disease. In this project we will define the mechanisms by which these sensing and response pathways occur, using E. coli as a model. The information obtained from this research should lead to new strategies to treat and prevent bacterial infections.
Genetic Dissection Of The Biogenesis And Function Of Type IV Fimbriae Of Pseudomonas Aeruginosa
Funder
National Health and Medical Research Council
Funding Amount
$407,545.00
Summary
Pseudomonas aeruginosa is a common bacterium which causes serious life-threatening infections of individuals with cystic fibrosis, AIDS or who have suffered severe burns or are undergoing cancer chemotherapy. This pathogen, and a number of other important infectious bacteria use surface filaments, called fimbriae, like grappling hooks to attach to the cells of the body and to move across host tissues. These fimbriae are produced in response to environmental conditions, and are assembled by a pro ....Pseudomonas aeruginosa is a common bacterium which causes serious life-threatening infections of individuals with cystic fibrosis, AIDS or who have suffered severe burns or are undergoing cancer chemotherapy. This pathogen, and a number of other important infectious bacteria use surface filaments, called fimbriae, like grappling hooks to attach to the cells of the body and to move across host tissues. These fimbriae are produced in response to environmental conditions, and are assembled by a process that is also used in the export of toxins and other pathogenic molecules. This project will characterise genes which specify and control this system, as a means to design better treatments against such bacteria, many of which are resistant to antibiotic treatment.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
Characterisation Of A Newly-discovered, Virulence-associated, Protein Secretion System Of Enteropathogenic E. Coli
Funder
National Health and Medical Research Council
Funding Amount
$582,149.00
Summary
The cell walls of bacteria act as a barrier to the export of any proteins they produce. We recently discovered a protein secretion system, which diarrhoea-causing strains of E. coli require to cause disease. The aim of this study is to characterise this secretory system, and discover how it functions and what it secretes. The knowledge obtained from this research will shed new light on how E. coli causes disease and could reveal novel methods to treat and prevent infections with this bacterium.
Role Of Novel Mobile Elements In The Infiltration Of Antibiotic Resistance Genes Into Clinical Isolates.
Funder
National Health and Medical Research Council
Funding Amount
$421,650.00
Summary
Bacteria have a remarkable ability to capture and spread antibiotic resistance genes. This phenomenon is a particular problem in our hospitals and in the community as multi-drug resistant pathogenic organisms have been selected over time as a result of the use of antibitoics. Moreover the incidence of resistance appears to be on the increase. Once resistant strains appear they can greatly complicate the treatment of infections and the eradication of such pathogens from a hospital is both difficu ....Bacteria have a remarkable ability to capture and spread antibiotic resistance genes. This phenomenon is a particular problem in our hospitals and in the community as multi-drug resistant pathogenic organisms have been selected over time as a result of the use of antibitoics. Moreover the incidence of resistance appears to be on the increase. Once resistant strains appear they can greatly complicate the treatment of infections and the eradication of such pathogens from a hospital is both difficult and costly. We have been working on the problem of how antibiotic resistance genes are spread for a number of years and have identified a novel genetic element that can capture resistance genes by a process of site-specific recombination. This element, the integron, is common in mutli-drug resistant clinical isolates. To be captured by an integron, an antibiotic resistance gene has to be part of a mobile element known as a gene cassette. Although the application of antibiotics acts to amplify pathogens that are resistant and favours their persistance in hospitals, it is generally recognized that neither the gene cassette nor the drug resistance gene evolve in the hospital. Rather, these genes make their way into human pathogens from bacteria that normally reside in other environments, for example soil or water. In this project, we will investigate one route by which drug resistance genes and integrons might find their way into clinically relevant strains and what the sources of the resistance genes and gene cassettes might be. A greater understanding of these processes will help in developing strategies to limit the spread of drug resistant bacteria into and around hospitals.Read moreRead less