Project description:Background: Salmonella Typhi and Salmonella Paratyphi A are the agents of enteric (typhoid) fever; both can establish chronic carriage in the gallbladder. Chronic Salmonella carriers are typically asymptomatic, intermittently shedding bacteria in the feces, and contributing to disease transmission. Detecting chronic carriers is of public health relevance in areas where enteric fever is endemic, but there are no routinely used methods for prospectively identifying those carrying Salmonella in their gallbladder. Methodology/Principal Findings: Here we aimed to identify biomarkers of Salmonella carriage using metabolite profiling. We performed metabolite profiling on plasma from Nepali patients undergoing cholecystectomy with confirmed S. Typhi or S. Paratyphi A gallbladder carriage (and non-carriage controls) using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOFMS) and supervised pattern recognition modeling. We were able to significantly discriminate Salmonella carriage samples from non-carriage control samples. We were also able to detect differential signatures between S. Typhi and S. Paratyphi A carriers. We additionally compared carriage metabolite profiles with profiles generated during acute infection; these data revealed substantial heterogeneity between metabolites associated with acute enteric fever and chronic carriage. Lastly, we found that Salmonella carriers could be significantly distinguished from non-carriage controls using only five metabolites, indicating the potential of these metabolites as diagnostic markers for detecting chronic Salmonella carriers. Conclusions/Significance: Our novel approach has highlighted the potential of using metabolomics to search for diagnostic markers of chronic Salmonella carriage. We suggest further epidemiological investigations of these potential biomarkers in alternative endemic enteric fever settings.
Project description:Typhoid fever, caused primarily by Salmonella enterica serovar Typhi (S. Typhi), is a life-threatening systemic disease responsible for significant morbidity and mortality worldwide. 3-5% of individuals infected with S. Typhi become chronic carriers due to bacterial persistence in the gallbladder. We have demonstrated that Salmonella forms biofilms on gallstones to establish gallbladder carriage. However, an in-depth molecular understanding of chronic carriage in the gallbladder, from the perspective of both the pathogen and host, is poorly defined. To examine the dynamics of the gallbladder in response to Salmonella infection, we performed transcriptional profiling in the mouse gallbladder at early (7 day) and chronic (21 day) time points. RNA-Seq revealed a shift from a Th1 pro-inflammatory response at 7 days post infection (DPI) towards an anti-inflammatory Th2 response by 21 DPI, characterized by increased levels of immunoglobulins and the Th2 master transcriptional regulator, GATA3. Additionally, bioinformatic analysis predicted the upstream regulation of characteristic Th2 markers including IL-4 and Stat6. Immunohistochemistry and FACS analysis confirmed a significant increase in lymphocytes, including T and B cells, at 21 DPI in mice with gallstones. Interestingly, Salmonella-specific CD4 T-cells were ten-fold higher in the gallbladder of mice with gallstones at 21 DPI. We speculate that the biofilm state allows Salmonella to resist the initial onslaught of the Th1 inflammatory response, while yet undefined events influence a switch in the host immunity towards a more permissive Type 2 response, enabling the establishment of chronic infection.
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.
Project description:Part of a study to characterise the two component regulatory system yehUT of Salmonella enterica serovar Salmonella Typhi and Typhimurium.