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Experimental infection of specific-pathogen-free mice with enterohemorrhagic Escherichia coli O157:H7
1Department of Microbiology, Chinese Academy of Preventive Medicine, Changping, Beijing.
Abstract:
By subcutaneous inoculation of 10(8) CFU of enterohemorrhagic E. coli O157:H7, specific-pathogen-free mice revealed most of the symptoms and histological changes observed in patients. The histological changes in intestine were mainly seen in the distal parts of small intestine and the cecum. Vacuolation of villi in the cecum was also observed. The histological changes in the kidneys of the infected mice were featured as the swollen epithelial cells of glomeruli and the marked thickening of glomerular capillaries with barely visible lumens. Unexpected findings in the bronchiole were characterized by sloughing of the epithelial cells of bronchiolar wall, leading to partial or complete obstruction of the lumens. Histological changes in the spleen, liver and lymphnodes were also observed. The bacteria were recovered from the feces, contents of small intestine, and samples taken from kidney, liver, heart, spleen, different parts of small intestine, cecum, and colon. By using peroxidase-antiperoxidase (PAP) assay with polyclonal antibodies against "O" antigen of E. coli O157:H7, it was observed that the samples taken from the brain, kidney, ileum, cecum, spleen, and liver gave positive reactions. Feces and contents of small intestine obtained from all of the infected animals were positive by occult blood test. These results show that the experimental infection of E. coli O157:H7 in this model is systemic in nature.
Insights
This study shows enterohemorrhagic Escherichia coli O157:H7 infection in mice causes symptoms similar to human patients. The bacteria spread systemically, affecting multiple organs including the kidneys and intestines.
Area of Science:
- Microbiology
- Pathology
- Animal Models
Background:
- Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a significant human pathogen.
- Understanding EHEC pathogenesis requires suitable animal models.
Purpose of the Study:
- To establish and characterize a mouse model for EHEC O157:H7 infection.
- To investigate the systemic spread and pathological effects of EHEC O157:H7.
Main Methods:
- Specific-pathogen-free mice were subcutaneously inoculated with EHEC O157:H7.
- Histopathological analysis was performed on various organs.
- Bacterial presence was confirmed using culture and peroxidase-antiperoxidase (PAP) assay.
- Occult blood testing was conducted on feces and intestinal contents.
Main Results:
- Infected mice exhibited symptoms and histological changes mirroring human EHEC infections, particularly in the distal small intestine and cecum.
- Kidney and bronchiole tissues showed significant pathological alterations.
- E. coli O157:H7 was detected in multiple organs, including brain, kidney, liver, and spleen, confirming systemic infection.
- Positive occult blood tests indicated gastrointestinal bleeding.
Conclusions:
- The mouse model successfully replicates key aspects of human EHEC O157:H7 infection.
- EHEC O157:H7 infection in this model is systemic, affecting various organs beyond the primary site of inoculation.