Summary auto-generated
This article investigates the survival and behavior of Salmonella enterica serovar Typhimurium strains in the mammalian gut environment. Researchers compared wild-type LT7 bacteria and isogenic mutants (LT7 carrying plasmids pHC79 and pHC20.2) using in vitro gut models to assess bacterial persistence. The study examined how gut-derived factors influence bacterial viability and recovery rates over time. Key experiments included culturing bacteria with and without intestinal tissue, measuring viable bacterial counts at multiple timepoints, and analyzing survival dynamics using standardized protocols. The research demonstrates differential survival patterns between the bacterial strains tested, with some strains showing enhanced persistence in the presence of gut tissue compared to controls without intestinal components. Results indicate that specific genetic elements and environmental conditions within the gut significantly affect Salmonella survival. The findings have implications for understanding bacterial pathogenesis and host-pathogen interactions during enteric infection.
Key findings
- Salmonella survival varies significantly between wild-type and plasmid-carrying strains when exposed to mammalian gut tissue
- Gut-derived environmental factors enhance or suppress bacterial viability depending on strain genotype
- LT7 strains with different plasmids (pHC79 vs pHC20.2) demonstrate distinct survival kinetics in gut models
- Bacterial recovery rates decrease over time but at different rates depending on presence of intestinal tissue
- Genetic elements encoded on the test plasmids influence Salmonella persistence in simulated gut conditions
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Abstract
A cosmid DNA library had been constructed previously from 40-kb fragments of genomic DNA from a virulent invasive strain of Salmonella enterica serotype Typhimurium (TML) in an avirulent hypo-invasive Typhimurium strain (LT7). Selection of invasive clones from the library was attempted by iterative passage through a rabbit ileal organ culture. After the fourth passage, a clone, designated LT7(pHC20uu.2), was isolated. Exposure to both gut tissue and Caco-2 cells enhanced the growth, invasiveness for gut and Caco-2 cells, and flagellin expression of LT7(pHC20uu.2) although its invasiveness was less than that of strain TML. Expression of appendages (surface structures c. 6070 nm diameter) was shown to play a role in but not to confer invasiveness, and was demonstrated in the absence of direct contact with eukaryotic cells. Exposure to gut tissue also affected the expression of several outer-membrane proteins (OMPs) in all four Salmonella strains TML, LT7, LT7(pHC79), LT7(pHC20uu.2) used in this work. As the genes involved in flagella, invasin and porin expression are distributed around the salmonella chromosome, it is possible that pHC20uu.2 encodes a pleiotropic regulator of genes involved in gastro-enteritic virulence and adaptation to the in-vivo gut environment. pHC20uu.2 mapped at c. centisome 25 on the salmonella chromosome close to, but distinct from, SPI-5.