Novel Compounds For Use As Inhibitors Of Virulence Of Human Pathogens
Funder
National Health and Medical Research Council
Funding Amount
$220,500.00
Summary
There is growing concern over the emergence of multi-drug resistant strains of bacteria which are no longer treatable with the current generation of antibiotics. This highlights the urgent need for development of the next generation of therapeutic agents to supplement or replace the current antibiotics. Our research team has identified a class of compounds which are naturally produced by a marine alga that may be effective in the control of bacterial pathogens. These compounds work by interferin ....There is growing concern over the emergence of multi-drug resistant strains of bacteria which are no longer treatable with the current generation of antibiotics. This highlights the urgent need for development of the next generation of therapeutic agents to supplement or replace the current antibiotics. Our research team has identified a class of compounds which are naturally produced by a marine alga that may be effective in the control of bacterial pathogens. These compounds work by interfering with the way many pathogens regulate the production of virulence traits. Some bacteria are able to signal members of their population by the specific uptake and recognition, through a receptor protein, of chemical cues they secrete into the environment. Accumulation of these cues or signals triggers expression of the genes that code for the virulence traits. Moreover, one particular class of these signal response proteins has been identified in many pathogens and has been shown to regulate protease production and production of a protective extracellular slime layer called a capsule. If one or more of these traits can be blocked, then the virulence of the bacterium can be reduced. We have preliminary data which demonstrates that the algal compounds do in fact prevent the expression of virulence traits and thus should be useful as new agents for the treatment of disease. The causative agents of cholera and severe gatroenteritis, Vibrio cholerae and V. parahaemolyticus respectively, have one or the other of these virulence traits, but the pathogen Vibrio vulnificus has all three and therefore is an excellent model pathogen. We propose to explore the ability of the algal compounds to specifically shut down expression of virulence factors with a long term aim for the development of these compounds as novel antimicrobial therapies for the post-antibiotic era.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
Antibiotic resistance increases mortality and costs in the Intensive Care Unit (ICU), but the impact of antibiotic therapy has not been adequately studied. We propose to characterise the behaviour of key elements of the bacterial microflora (resistant bacteria and major resistance genes) in response to antibiotics. We have developed new rapid diagnostics to harness these data and this proposal has the potential to greatly improve diagnostic speed and accuracy and thus clinical outcomes.
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
MOLECULAR ANALYSIS OF VIRULENCE FACTORS OF GROUP B STREPTOCOCCI
Funder
National Health and Medical Research Council
Funding Amount
$211,527.00
Summary
Streptococcus agalactiae, more commonly referred to as group B streptococcus (GBS), is the commonest cause of life-threatening infection (specifically bacteraemia, pneumonia and meningitis) in neonates. Mortality is high even in developed countries where antimicrobial therapy is readily available. In spite of the importance of GBS disease, the precise molecular mechanisms whereby the organism colonizes, invades and damages host tissues are poorly understood. The long term goal of this project is ....Streptococcus agalactiae, more commonly referred to as group B streptococcus (GBS), is the commonest cause of life-threatening infection (specifically bacteraemia, pneumonia and meningitis) in neonates. Mortality is high even in developed countries where antimicrobial therapy is readily available. In spite of the importance of GBS disease, the precise molecular mechanisms whereby the organism colonizes, invades and damages host tissues are poorly understood. The long term goal of this project is to gain a complete understanding of the pathogenesis of GBS disease and to apply this to development of improved preventative strategies. We propose to carry out a comprehensive molecular characterization of genes encoding putative GBS virulence determinants, with particular reference to those which encode the capacity to adhere to and invade host cells. GBS carrying defined mutations in these genes will be constructed and their virulence will be compared with that of the otherwise isogenic parental GBS. This will enable us to determine the precise contribution of each putative virulence factor to the pathogenesis of disease. Moreover, proteins shown to be important in this process will be tested for vaccine potential.Read moreRead less
Characterisation Of Community Methicillin-resistant Staphylococcus Aureus And Their Control In Remote Communities
Funder
National Health and Medical Research Council
Funding Amount
$300,777.00
Summary
Before the introduction of antibiotics Staphylococcus aureus, the golden staph , was the major cause of infections in hospitals. Although the introduction of antibiotics helped control the organism it has gradually acquired resistance until strains have emerged which can only be treated with vancomycin. Consequently staphs have again emerged as a major hospital pathogen. The emergence of these multiply resistant strains corresponded to them acquiring methicillin resistance and consequently they ....Before the introduction of antibiotics Staphylococcus aureus, the golden staph , was the major cause of infections in hospitals. Although the introduction of antibiotics helped control the organism it has gradually acquired resistance until strains have emerged which can only be treated with vancomycin. Consequently staphs have again emerged as a major hospital pathogen. The emergence of these multiply resistant strains corresponded to them acquiring methicillin resistance and consequently they have come to be known as methicillin-resistant Staphylococcus aureus or MRSA. Soon after the emergence of MRSA the hospitals of Western Australia (WA) developed a policy to prevent introduced MRSA from becoming established in its hospitals. Although this has been successful the policy is now under threat with the emergence of MRSA in remote WA Aboriginal communities. Aboriginals in these communities have a large number of infections which are usually treated empirically. This can result in the selection of antibiotic resistant bacteria if they are present. Consequently, it is planned to regularly screen Aboriginal communities which are known to have a high prevalence of MRSA and recommend antibiotic prescribing which will not select for any resistant staphylococci carried by a person. This is possible because the community MRSA are still susceptible to some anti-staphylococcal drugs. If this program is shown to reduce the prevalence of MRSA in the communities then the program will be extended to other communities. Community MRSA are now being reported from other Australian states and it is planned to study these to see if they are related to the WA strains. The community isolates will be studied to assess their potential to acquire additional antibiotic resistances. As some strains are known to be more of a threat to hospitals than others methods will be investigated to develop rapid methods for detecting them.Read moreRead less
Chronic Bacterial Infection And The Generation Of T Cell Memory: Implication For Vaccination Against Tuberculosis
Funder
National Health and Medical Research Council
Funding Amount
$547,970.00
Summary
Two million people die from tuberculosis (TB) each year. The immune system is unable to eradicate the TB bacterium, and the type of immune response needed to protect against the disease is poorly understood. We will use animal models of TB infection and sophisticated immunological techniques to decipher how the TB bacterium interacts with the immune sytem and causes disease. We will also develop new TB vaccines that aim to boost the immune response in the lung, the main site of TB infection.
Streptococcus pneumoniae (the pneumococcus) is an important human pathogen, which is responsible for the deaths of millions of children each year in developing countries. The high morbidity and mortality associated with pneumococcal disease is also being exacerbated by the rate at which this organism is acquiring resistance to multiple antibiotics. Existing pneumococcal polysaccharide vaccines are poorly immunogenic in young children and only provide cover against a limited range of serotypes. S ....Streptococcus pneumoniae (the pneumococcus) is an important human pathogen, which is responsible for the deaths of millions of children each year in developing countries. The high morbidity and mortality associated with pneumococcal disease is also being exacerbated by the rate at which this organism is acquiring resistance to multiple antibiotics. Existing pneumococcal polysaccharide vaccines are poorly immunogenic in young children and only provide cover against a limited range of serotypes. Serotype coverage is even lower in the more immunogenic conjugate vaccines currently being developed; these will also be very expensive, thereby limiting their use in developing countries, where the need for effective paediatric vaccines is greatest. Pneumococci produce a variety of proteins which are important in causing disease, but the relative contribution of these factors at each stage of the infection process remain to be determined. Moreover, virtually nothing is known of the mechanism whereby these virulence factors are regulated in response to the external environment of the bacterium. In view of this, we are conducting a comprehensive examination of the mechanisms of pathogenesis of pneumococcal disease, with particular reference to the role of putative virulence proteins. This information is being used to develop cheap and effective vaccines based on pneumococcal protein antigens common to all serotypes.Read moreRead less
Plasmids are extra mini-chromosomes that are present in many bacteria. They carry information that enables their hosts to survive and prosper in hostile environments. Plasmids are able to spread rapidly between bacteria, ensuring that the information they carry is rapidly disseminated throughout bacterial populations. Many plasmids carry information that increases the virulence of their host bacteria, because it adds to their repertoire of toxins and other adjuncts to invasiveness and colonisati ....Plasmids are extra mini-chromosomes that are present in many bacteria. They carry information that enables their hosts to survive and prosper in hostile environments. Plasmids are able to spread rapidly between bacteria, ensuring that the information they carry is rapidly disseminated throughout bacterial populations. Many plasmids carry information that increases the virulence of their host bacteria, because it adds to their repertoire of toxins and other adjuncts to invasiveness and colonisation, or enables them to survive in the presence of antibiotics. The emergence of multi-drug resistant bacteria and the rapid spread of the ability of bacteria to withstand most antibiotics available to date were mediated by plasmids. Plasmids also carry information that ensures their own survival. The consequence of this is that their bacterial hosts retain the plasmids, even when it is no longer beneficial to do so. For example, plasmids carrying information for resistance to antibiotics are not lost when their bacterial hosts grow in the absence of antibiotics. This is because plasmids have control systems, which ensure that on the one hand, replication of the plasmid keeps pace with the replication of its host, and on the other hand that the plasmid does not produce so many copies of itself that it overwhelms its host. This project examines the intricate regulatory system that a group of antibiotic-resistance plasmids uses to ensure that on average each plasmid molecule is replicated once per bacterial cell cycle. This system uses an antisense RNA, a tertiary RNA structure (pseudoknot) that acts as a translational switch, and a protein that interacts with different sequences on the plasmid to initiate replication. Detailed knowledge of the processes underlying this complex system is required if we are to develop new treatments that will lead to elimination of antibiotic-resistance and virulence-contributing plasmids from populations of pathogenic bacteria.Read moreRead less
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