disarming type 3 secretion- elucidating the mechanism of action for aurodox

Antibiotics have been used for many years and are central to the treatment of many common bacterial infections1. However, because antibiotics kill bacteria, there is a strong selection for mutants, slightly different from the parental type of bacteria: a new resistant form. These resistant bacteria are no longer susceptible to common antibiotics resulting in an urgent need for new alternative forms of treatment2. Of greatest concern are the Gram-negative family of bacteria that pose the most serious threats to human, animal and plant health. The management and treatment of these infections falls within the "Tackling infections" strategic theme of the UKRI priority areas. The challenge we are addressing is how to treat infections that can rapidly adapt to traditional antibiotics. One possibility is to use anti-virulence compounds that "disarm" bacteria rather than killing them, generating less selection for resistant mutants3. This approach is particularly attractive to deal with toxin-producing bacteria because their treatment with traditional antibiotics is controversial including reports of increased toxin production and more severe symptoms4. By not killing the bacteria, toxin release is avoided. The organism we work on is Escherichia coli O157:H7 (EHEC), a zoonotic pathogen that colonises cattle and enters the food chain causing life-threatening disease and a variety of complications through the production of shiga toxin. There is currently no effective vaccine or antibiotic treatment recommended for the treatment of EHEC infections5. Our group has been working on a "re-discovered" compound called aurodox which was initially characterised in the early 1970s6. Treatment of EHEC with aurodox results in a strong repression of the type three secretion system (T3SS), used by the bacteria as the primary mechanism to attach to host intestinal cells7. Under a nearly completed RCUK grant, we have shown that aurodox can prevent the pathology associated with EHEC infections, specifically shiga toxin-mediated kidney damage and weight loss in mice. This is the first demonstration that aurodox protects against EHEC-type disease in an animal model and paves the way for translation into humans. However, three major questions remain: firstly, how does aurodox work to suppress the expression of the T3SS, secondly, can aurodox be used to treat other problematic infections that also rely on the T3SS for virulence, and, thirdly, can we generate new derivates of aurodox. These three questions are the focus of the current proposal. Why are these questions important to address? Firstly, knowledge of the mechanism of action is an important piece of information that pharmaceutical companies often insist on before they are prepared to invest in clinical trials. Understanding the mechanism helps the further refinement and development of the compound. Secondly, demonstrating the ability of aurodox to prevent infections in other pathogens would widen the commercial potential of the treatment and help attract investment that is essential for translation to the clinic/field. Finally, generating new derivates would provide unique intellectual property and can help increase the potency and specificity of the compound. We also believe the results of this science would generate world-class science that would be of broad interest to the community.