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Histopathology of mixed anaerobic intraabdominal infection in mice
Abstract:
This study characterized acute peritonitis and chronic abscess formation resulting from experimental mixed anaerobic infection with Bacteroides melaninogenicus and Fusobacterium necrophorum. At intervals after infection liver and spleen samples were obtained, fixed, and processed for histological examination. An acute to chronic infection progressed in mice infected with this mixture of anaerobic bacteria, whereas, no infection resulted when either organism was injected alone. Acute inflammatory cell infiltrates were noted in tissue samples at 12 h postinfection. Small, discrete areas of liver cell necrosis with neutrophilic infiltrates were observed as early as 24 h. By 48 h after infection the liver parenchyma was infiltrated with both acute and chronic inflammatory cells, with moderate to severe hepatocyte degeneration recognized at 72 h. Large intrahepatic abscesses were present in the subphrenic (upper lobe) area 2 to 6 weeks after experimental infection.
Insights
This study shows that a mixed anaerobic bacterial infection with Bacteroides melaninogenicus and Fusobacterium necrophorum causes acute peritonitis and chronic liver abscesses in mice. Neither bacterium alone caused infection, highlighting the synergistic effect in this animal model.
Area of Science:
- Microbiology
- Pathology
- Veterinary Medicine
Background:
- Anaerobic bacterial infections can lead to severe complications.
- The synergistic effects of mixed anaerobic infections are not fully understood.
- Bacteroides melaninogenicus and Fusobacterium necrophorum are common anaerobic pathogens.
Purpose of the Study:
- To characterize the progression of acute peritonitis and chronic abscess formation.
- To investigate the role of a mixed anaerobic infection in liver pathology.
- To determine the necessity of both Bacteroides melaninogenicus and Fusobacterium necrophorum for infection.
Main Methods:
- Experimental infection of mice with a mixture of Bacteroides melaninogenicus and Fusobacterium necrophorum.
- Collection and histological examination of liver and spleen samples at various time points post-infection.
- Assessment of inflammatory responses and tissue damage.
Main Results:
- A mixed infection led to progressive acute to chronic disease, while single organisms did not cause infection.
- Acute inflammatory cell infiltrates were observed within 12 hours post-infection.
- Liver cell necrosis and degeneration, along with intrahepatic abscess formation, were evident by 72 hours and persisted for weeks.
Conclusions:
- A synergistic interaction between Bacteroides melaninogenicus and Fusobacterium necrophorum is essential for causing acute peritonitis and chronic liver abscesses.
- This experimental model provides insights into the pathogenesis of mixed anaerobic infections.
- The findings have implications for understanding and treating similar infections in clinical settings.