Grant: CIHR Fellowship

Each year, diarrheal illnesses affect 1.7 billion people and claim the lives of more than 700,000 children worldwide. Many cases of diarrhea are caused by a category of bacteria known as attaching and effacing (A/E) pathogens, which includes both bacteria that infect humans (such as enterohemorrhagic E. coli - the cause of "hamburger disease") and bacteria that infect mice (such as Citrobacter rodentium). One major hurdle that A/E pathogens must overcome in order to infect their hosts is the presence of the intestinal microbiota, which is the community of trillions of bacteria present in mammals' digestive tracts. The microbiota can interfere with a pathogen's ability to infect its host by competing for nutrients, boosting the host's immune system, or directly interfering with the pathogen's growth. The microbiota play a large role in determining whether A/E pathogens succeed in infecting their hosts. Disruption of the microbiota (for example, by treatment with antibiotics) can make the difference between recovery and death for mice infected with C. rodentium. The strong impact of the microbiota on the success of A/E pathogens suggests that the pathogens have evolved methods to sense and respond to the presence of the microbiota, yet the effects of microbiota on A/E pathogen behaviour are largely unknown. My research will examine how A/E pathogens respond to the presence of intestinal microbiota and the chemicals they produce by determining which of the pathogens' genes are turned on or turned off in the presence of the microbiota. I will then go on to check whether any of these genes are important for C. rodentium's ability to infect mice. This research will improve our understanding of how gut microbiota communicate with pathogens like E. coli, which is important because the chemical signals made by the microbiota could potentially be developed into new drugs to prevent or treat bacterial infections.