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Early colonic lesions in experimental Shigella infection in rhesus monkeys: revisited
Abstract:
Rhesus monkeys (Macaca mulatta), given 3 X 10(8) to 5 X 10(10) Shigella flexneri 2a orally, developed signs of acute shigellosis within 24 hours. A diffuse acute colitis was well established at 48 hours. The inflammatory reaction was confined to the mucosa. The submucosa showed only edema. The shigellae were found predominantly in the columnar cells of the surface epithelium, less frequently in those of the crypt, and least frequently in the lamina propria. Shigella bacilli invaded the columnar cells from the intestinal lumen. The bacilli multiplied within epithelial cells and spread laterally to adjacent epithelial cells and penetrated the lamina propria. The bacterial invasion affected epithelial cells unevenly and resulted in the disappearance of goblet cells and pyknotic shrinkage of the surface epithelial cells. Epithelial cells had abnormal and accelerated exfoliation which resulted in multifocal epithelial defects. There was a distinct correlation between the quantity of bacilli present in tissues and the intensity of the inflammatory response. The small intestines were spared.
Insights
Oral infection with Shigella flexneri 2a in rhesus monkeys causes acute colitis. Shigella invasion of epithelial cells correlates with inflammation intensity and epithelial defects.
Area of Science:
- Microbiology
- Pathology
- Immunology
Background:
- Shigellosis is a significant cause of bacterial dysentery.
- Understanding the pathogenesis of Shigella infection is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the pathological changes and bacterial distribution in rhesus monkeys following oral Shigella flexneri 2a infection.
Main Methods:
- Rhesus monkeys were orally inoculated with varying doses of Shigella flexneri 2a.
- Clinical signs, gross pathology, and histopathology of the colon were assessed at 24 and 48 hours post-infection.
Main Results:
- Oral Shigella flexneri 2a infection induced acute colitis within 24-48 hours.
- Shigella bacilli primarily invaded and multiplied within epithelial cells, leading to cell damage and accelerated exfoliation.
- Inflammation was confined to the mucosa, with a direct correlation between bacterial load and inflammatory response intensity.
Conclusions:
- Shigella flexneri 2a invades and damages colonic epithelial cells, causing acute colitis.
- The observed pathology highlights the role of epithelial cell invasion and host inflammatory response in shigellosis pathogenesis.