S. Typhi in Water and Role of Microbial Partners

France Daigle of the University of Montreal in Canada will identify the microorganisms that enable the survival of the typhoid fever-causing bacterium, Salmonella enterica serovar Typhi, at low levels in water, and thereby enhances disease spread. Typhoid fever spreads through contaminated food and water, and results in over 125,000 deaths annually worldwide. S. Typhi are so-called auxotrophic bacteria because they rely on an external source of the essential amino acids that they need to grow. Microbial interactions may provide nutrients and also increase bacterial fitness and support persistence by protecting them from the environment, thereby increasing the rate of disease transmission. They will assemble a microbial community in water consisting of three components: one protozoan (from a group known to promote bacterial survival); a defined consortium of bacteria representative of the human fecal microbiota; and fluorescently-tagged S. Typhi. They will evaluate the ability of S. Typhi to grow in these microcosms, and how they grow, such as in biofilms or inside the protozoa. They will also determine whether these persistent S. Typhi are better able to infect and survive in human cells. Finally, water samples from an endemic region in East Africa will be analyzed for the presence of S. Typhi and identified beneficial microbial partners using quantitative PCR.