Related Experiment Video
Updated: Oct 2, 2026
Colon Ascendens Stent Peritonitis (CASP) - a Standardized Model for Polymicrobial Abdominal Sepsis
Published on: December 18, 2010
Early bacterial and inflammatory responses to antibiotic therapy in a model of polymicrobial peritonitis in rats
Philippe Montravers1, Jacqueline Mohler, Laurence Maulin
1INSERM CRI 4U002D, Hôpital Bichat, Paris, France.
Abstract:
OBJECTIVE: To assess the consequences of different more or less selective treatments on the microbiological and inflammatory responses within the peritoneum. METHODS: The early effects of various antibiotic regimens were evaluated in a model of polymicrobial peritonitis with specifically prepared organisms. Six regimens (amoxycillin plus gentamicin, pefloxacin, ornidazole, pefloxacin plus ornidazole, imipenem and imipenem plus gentamicin) were evaluated at 24 h and 3 days in a non-fatal model of peritonitis in rats achieved by implantation of a capsule containing Escherichia coli, Bacteroides fragilis and Enterococcus faecalis. RESULTS: Therapies that disregarded several organisms were associated with persistence of the strains and an increased peritoneal inflammatory response within the peritoneum. In contrast, therapies active against Enterobacteriaceae and anaerobes were associated with decreases of all the inoculated organisms and a smaller inflammatory response. CONCLUSION: Therapies that disregarded the microorganisms implicated in peritoneal infection are associated with delayed bacterial eradication. The persistence of these organisms within the peritoneal fluid might be involved in prolonged peritoneal inflammation. Although it disregards enterococci, the standard therapy, represented by therapy against Enterobacteriaceae and anaerobes, demonstrates satisfactory effects towards all the inoculated organisms. This apparent contradiction could be related to mechanisms of bacterial synergy.
Insights
Antibiotic treatments that ignore specific bacteria in peritonitis models prolong inflammation. Broad-spectrum therapies targeting key pathogens like Enterobacteriaceae and anaerobes effectively reduce bacterial load and inflammation, even if they don't cover all species.
Area of Science:
- Microbiology
- Pharmacology
- Immunology
Background:
- Peritonitis involves complex microbial communities and significant inflammation.
- Antibiotic selection impacts microbiological and inflammatory outcomes in peritoneal infections.
Purpose of the Study:
- To evaluate the effects of diverse antibiotic regimens on peritoneal microbiology and inflammation.
- To assess the consequences of selective versus broad-spectrum antibiotic treatments in polymicrobial peritonitis.
Main Methods:
- A rat model of polymicrobial peritonitis was established using Escherichia coli, Bacteroides fragilis, and Enterococcus faecalis.
- Six different antibiotic regimens were administered and evaluated at 24 hours and 3 days.
- Microbiological burden and peritoneal inflammatory markers were assessed for each treatment group.
Main Results:
- Treatments with limited organism coverage led to persistent bacterial strains and heightened peritoneal inflammation.
- Antibiotic regimens targeting Enterobacteriaceae and anaerobes resulted in significant reduction of all inoculated organisms.
- These broad-spectrum therapies were associated with a diminished inflammatory response compared to selective treatments.
Conclusions:
- Inadequate antibiotic coverage delays bacterial eradication and may prolong peritoneal inflammation.
- Targeting key pathogens like Enterobacteriaceae and anaerobes is crucial for effective peritonitis management.
- Bacterial synergy may explain why standard therapies, despite not covering all species, show satisfactory outcomes.
