Comparative Analysis of Live, Heat-inactivated, and Electron Beam Inactivated Salmonella Typhimurium Infection in Human Host Cells

Salmonella Typhimurium continues to be a leading cause of human gastroenteritis worldwide. This organism is a facultative intracellular pathogen, meaning that it is able grow and reproduce within the host cell it inhabits. S. Typhimurium has the ability to invade and replicate within human intestinal epithelial cells, which in turn causes induced cell death or apoptosis. The human intestinal epithelial cells, HCT-8, were challenged with live, heat inactivated, and electron beam inactivated S. Typhimurium for various time points. Infected cell monolayers were collected for RNA extractions, and Real-time PCR was performed on the samples to analyze differential gene expression. Genes of the host cell that were expected to be differentially expressed were shortlisted and Real-Time PCR analysis was performed. Internalized Salmonella within the host cell was unable to be successfully visualized using fluorescent light microscopy. However, differential gene expression for a common transcriptional regulator and inflammatory chemokine were observed to be expressed significantly higher in response to e-beam inactivated Salmonella infection. Genes coding for extracellular and intracellular pattern-recognition receptors of the host cells were shown to be up-regulated in response to e-beam inactivated Salmonella infection at 4 and 24 hours, but were not statistically significant. Additional studies must be conducted to definitively confirm e-beam irradiated Salmonella has the ability to invade human host cells

Deletions in the pyruvate pathway of Salmonella Typhimurium alter SPI1-mediated gene expression and infectivity

BACKGROUND: Salmonella enterica serovar Typhimurium is a major foodborne pathogen worldwide. S. Typhimurium encodes type III secretion systems via Salmonella pathogenicity islands (SPI), producing the major effector proteins of virulence. Previously, we identified two genes of Salmonella pyruvate metabolism that were up-regulated during chicken cell infection: pyruvate formate lyase I (pflB) and bifunctional acetaldehyde-CoA/alcohol dehydrogenase (adhE). We were therefore interested in examining the role these genes may play in the transmission of Salmonella to humans. METHODS: Mutant strains of Salmonella with single gene deletions for pflB and adhE were created. Invasion and growth in human HCT-8 intestinal epithelial cells and THP-1 macrophages was examined. Quantitative PCR was performed on 19 SPI-1 genes. RESULTS: In HCT-8 cells, both mutant strains had significantly higher intracellular counts than the wild-type from 4 to 48 h post-infection. Various SPI-1 genes in the mutants were up-regulated over the wild-type as early as 1 h and lasting until 24 h post-infection. In THP-1 cells, no significant difference in internal Salmonella counts was observed; however, SPI-1 genes were largely down-regulated in the mutants during the time-course of infection. We also found five SPI-1 genes - hilA, hilC hilD, sicP and rtsA - which were up-regulated in at least one of the mutant strains in log-phase broth cultures alone. We have therefore identified a set of SPI-1 virulence genes whose regulation is effected by the central metabolism of Salmonella

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population