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Updated: Apr 19, 2026
High-throughput Assay to Phenotype Salmonella enterica Typhimurium Association, Invasion, and Replication in Macrophages
Published on: August 11, 2014
The frequency and duration of Salmonella-macrophage adhesion events determines infection efficiency
Sarra Achouri1, John A Wright2, Lewis Evans3
1Department of Physics, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, UK.
Abstract:
Salmonella enterica causes a range of important diseases in humans and a in a variety of animal species. The ability of bacteria to adhere to, invade and survive within host cells plays an important role in the pathogenesis of Salmonella infections. In systemic salmonellosis, macrophages constitute a niche for the proliferation of bacteria within the host organism. Salmonella enterica serovar Typhimurium is flagellated and the frequency with which this bacterium collides with a cell is important for infection efficiency. We investigated how bacterial motility affects infection efficiency, using a combination of population-level macrophage infection experiments and direct imaging of single-cell infection events, comparing wild-type and motility mutants. Non-motile and aflagellate bacterial strains, in contrast to wild-type bacteria, collide less frequently with macrophages, are in contact with the cell for less time and infect less frequently. Run-biased Salmonella also collide less frequently with macrophages but maintain contact with macrophages for a longer period of time than wild-type strains and infect the cells more readily. Our results suggest that uptake of S. Typhimurium by macrophages is dependent upon the duration of contact time of the bacterium with the cell, in addition to the frequency with which the bacteria collide with the cell.
Insights
Bacterial motility significantly impacts Salmonella Typhimurium infection efficiency. Longer contact times with host macrophages, not just collision frequency, enhance bacterial invasion and proliferation, crucial for understanding salmonellosis.
Area of Science:
- Microbiology
- Infectious Diseases
- Cell Biology
Background:
- Salmonella enterica causes significant human and animal diseases.
- Bacterial adhesion, invasion, and survival within host cells are key to Salmonella pathogenesis.
- Macrophages are critical host cells for Salmonella proliferation during systemic infections.
Purpose of the Study:
- To investigate the role of bacterial motility in Salmonella Typhimurium infection efficiency.
- To compare the infection dynamics of wild-type and motility mutant strains.
- To determine the relationship between bacterial-host cell contact and invasion.
Main Methods:
- Population-level macrophage infection experiments.
- Direct imaging of single-cell infection events.
- Comparison of wild-type Salmonella Typhimurium with non-motile and run-biased mutants.
Main Results:
- Non-motile and aflagellate Salmonella showed reduced collision frequency, shorter contact times, and lower infection rates.
- Run-biased Salmonella had reduced collision frequency but longer contact times, leading to increased infection.
- Macrophage uptake of Salmonella Typhimurium depends on both collision frequency and duration of contact.
Conclusions:
- Bacterial motility, specifically flagellar function, influences Salmonella's ability to infect macrophages.
- The duration of bacterial-host cell contact is a critical factor for Salmonella invasion.
- Understanding these dynamics can inform strategies against Salmonella infections.
