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Updated: Nov 15, 2025
Author Spotlight: Advancements in Understanding and Combatting Shigella Infections
Published on: February 9, 2024
Plaque Assay to Determine Invasion and Intercellular Dissemination of Shigella flexneri in TC7 Human Intestinal
Atin Sharma1,2,3, Andrea Puhar1,2,3
1The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå, Sweden.
Abstract:
Shigella flexneri invades the epithelial cells lining the gut lumen and replicates intracellularly. The specialized Type III Secretion System (T3SS) and its effector proteins, encoded on a large virulence plasmid, assist the bacterium to gain access to the cytosol. Thereafter Shigella disseminates to neighboring cells in an epithelial layer without further extracellular steps. Host cell lysis occurs when these bacteria have extensively replicated in the target cell cytosol. Here we describe a simple method to qualitatively as well as quantitatively study the capacity of Shigella to invade and disseminate within an epithelium by assessing the number and size of plaques representing the dead cells in a monolayer of TC7 cells. This classical protocol follows a simple approach of infecting the monolayers of epithelial cell lines with Shigella and visualizing the dead cells as plaques formed against a stained background.
Insights
This study presents a straightforward method to assess Shigella flexneri
Area of Science:
- Microbiology
- Cell Biology
- Infectious Diseases
Background:
- Shigella flexneri invades gut epithelial cells and replicates intracellularly.
- The Type III Secretion System (T3SS) facilitates bacterial entry into the host cell cytosol.
- Shigella spreads between cells without extracellular stages, leading to host cell lysis.
Purpose of the Study:
- To develop a simple method for studying Shigella invasion and dissemination.
- To quantitatively and qualitatively assess bacterial capacity to damage epithelial cells.
Main Methods:
- Infection of TC7 cell monolayers with Shigella flexneri.
- Visualization of dead cells as plaques against a stained background.
- Assessment of plaque number and size to determine invasion and dissemination efficiency.
Main Results:
- The described method allows for qualitative and quantitative analysis of Shigella's epithelial cell invasion and spread.
- Plaque formation directly correlates with the extent of bacterial replication and host cell damage.
- This protocol provides a reliable measure of Shigella's pathogenic potential.
Conclusions:
- A simple, classical plaque assay effectively evaluates Shigella invasion and dissemination.
- This method aids in understanding Shigella pathogenesis and evaluating potential therapeutics.
