Investigating the Effects of Ciprofloxacin on Intra-Macrophage Salmonella

Abstract Salmonella enterica is an intracellular pathogen capable of evading immune killing by surviving within immune cells such as macrophages. Further, increasing resistance to fluoroquinolones has led to both non-typhoidal Salmonella and Salmonella Typhi being listed as WHO high priority pathogens. There is therefore a need to understand how Salmonella is able to survive the joint effects of antibiotics and immune cells, yet these two factors are often studied in isolation. As a result, our understanding of how antibiotics affect molecular processes of intra-macrophage Salmonella, or how macrophages influence antibiotic survival is incomplete. This project therefore aims to understand the role of the fluoroquinolone ciprofloxacin in intra-macrophage survival of S. enterica serovar Typhimurium using advanced microscopy techniques that allow direct visualisation during macrophage infection. This project firstly aims to investigate the dynamics of ciprofloxacin target proteins in intracellular bacteria and how this affects DNA damage. Similarly, this project will also investigate how the combined effects of ciprofloxacin and the macrophage environment can influence two mechanisms of antibiotic treatment failure: resistance and persistence. By providing real-time data at single-cell resolution, this project will identify factors that may affect antibiotic effectiveness and provide novel insights into bacterial processes during Salmonella infection. BBSRC Priority Areas Combatting Antimicrobial Resistance: this project will improve our understanding of how antibiotics impact intracellular bacteria, including through live single cell visualisation. This project will also help to understand how macrophages can impact antibiotic treatment by causing mutagenesis or inducing antibiotic persistence. Technology Development for the Biosciences: to the best of our knowledge, this project represents some of the first applications of single molecule tracking within intracellular bacteria, a technique developed by the Uphoff lab. This project will involve optimisation of the protocol to make accurate measurements of protein dynamics within intra-macrophage Salmonella.