Pathoadaptive Alteration of Salmonella Biofilm Formation in Response to the Gallbladder Environment

Chronic carriers are the main reservoirs for the spread of typhoid fever in regions of endemicity.Salmonella Typhi forms biofilms on gallstones in order to persist. A strain with enhanced biofilm-forming ability was recovered after a nine-month chronic-carriage mouse study. After sequencing this strain and recreating some of the mutations, we could not duplicate the phenotype. The isolate did show a difference in flagella, a preference to bind to cholesterol, and a systemic virulence defect. Finally, gallbladder conditions were simulatedin vitro . After 60 days, there was a 4.5-fold increase in hyperbiofilm isolates when a gallstone was present. These results indicate thatSalmonella spp. can undergo genetic changes that improve persistence in gallbladder albeit at the cost of decreased virulence.