Project description:Many clinically relevant bacterial pathogens are encapsulated, as exemplified by Salmonella enterica serovar Typhi. S. Typhi, the causative agent of the life-threatening systemic disease enteric fever, expresses Vi as the outermost surface glycan that protects the bacteria from host immune responses. Multidrug-resistant (MDR) and extensively drug-resistant (XDR) S. Typhi strains, as well as Vi variants, are widespread globally. Our WGS analyses indicate that almost all S. Typhi clinical isolates are susceptible to rifamycins and azithromycin. Rifampin, even at sub-MIC levels, eliminates the protective capsule Vi, a process referred to as ‘decapsulation’, thereby enhancing bacterial clearance. Antibiotic-mediated decapsulation of S. Typhi appears specific to rifamycins, since azithromycin does not decapsulate S. Typhi. Rifampin mediated decapsulation occurs at the transcriptional level, where both high AT content and specific RpoB residues play a crucial role. Rifampin also effectively decapsulates Vi variants, which accounts for 1 in 5 S. Typhi isolates at the global level. A mechanistic explanation for rifampin mediated decapsulation of S. Typhi appears to be applicable to other encapsulated pathogens, including S. Paratyphi C.
Project description:Salmonella enterica subsp. enterica contains more than 2,600 serovars of which four are of major medical relevance for humans. While the typhoidal serovars (Typhi and Paratyphi A) are human-restricted and cause enteric fever, non-typhoidal Salmonella serovars (Typhimurium and Enteritidis) have a broad host range and predominantly cause gastroenteritis. In this study, we compared the core proteomes of Salmonella Typhi, Paratyphi A, Typhimurium and Enteritidis using contemporary proteomics. Five isolates, covering different geographical origins, and one reference strain per serovar were grown in vitro to the exponential phase. Protein levels of orthologous proteins between serovars were compared and subjected to gene ontology term enrichment and inferred regulatory interactions. Differential expression of the core proteomes of the typhoidal serovars appears mainly related to cell surface components and, for the non-typhoidal serovars, to pathogenicity. Our findings may guide future development of novel diagnostics and vaccines, and understanding of disease progression.
Project description:Part of a study to characterise the two component regulatory system yehUT of Salmonella enterica serovar Salmonella Typhi and Typhimurium.
Project description:Bacterial pathogens causing systemic disease commonly evolve from organisms associated with localized infections but differ from their close relatives in their ability to overcome mucosal barriers by mechanisms that remain incompletely understood. Here we investigated whether acquisition of a regulatory gene, tviA, contributed to the ability of Salmonella enterica serotype Typhi to disseminate from the intestine to systemic sites of infection during typhoid fever. To study the consequences of acquiring a new regulator by horizontal gene transfer, tviA was introduced into the chromosome of S. enterica serotype Typhimurium, a closely related pathogen causing a localized gastrointestinal infection in immunocompetent individuals. Modulation of gene expression by TviA in serotype Typhi and Typhimurium was determined by profiling and found to be very comparable. Expression of flagellin, a pathogen associated molecular pattern (PAMP), was repressed by TviA when bacteria were grown at osmotic conditions encountered in tissue, but not at higher osmolarity present in the intestinal lumen. TviA-mediated flagellin repression enabled bacteria to evade sentinel functions of human model epithelia and resulted in increased bacterial dissemination to the spleen in a chicken model.
Project description:Part of a study to characterise the two component regulatory system yehUT of Salmonella enterica serovar Salmonella Typhi and Typhimurium. 24 Samples examined, 12 of strain Salmonella Typhi BRD948 and 12 of strain Salmonella Typhimurium ST4/74.