A standardised and reproducible model of intra-abdominal infection and abscess formation in rats

Abstract

Objective: To develop a standardised and reproducible model of intra-abdominal infection and abscess formation in rats. Design: Experimental study. Setting: University hospital, The Netherlands. Subjects: 36 adult male Wistar rats. Interventions: In 32 rats, peritonitis was produced using two different concentrations of Escherichia coli (E. coli) and Bacteroides fragilis (B. fragilis) incorporated in fibrin clots (E. coli: 1 x 105 colony forming units (CFU)/ml or 1 x 108 CFU/ml, B. fragilis: 1 x 108 CFU/ml). Four rats with fibrin clots without bacteria served as uninfected controls. Main outcome measurements: Macroscopy and bacterial counts in peritoneal fluid, blood, and fibrin clots after 24 hours, 4 days, 7 days, and 4 weeks. Results: Macroscopically, there were signs of intra-abdominal infection and abscesses. With the higher starting concentration of E. coli, macroscopic signs were more pronounced and in nearly all rats bacterial counts in peritoneal fluid and fibrin clots showed persistently high numbers of E. coli and B. fragilis for at least 7 days (E. coli - 2 x 103 to 1 x 106 CFU/ml and 5 x 107 to 9 x 108 CFU/clot; B. fragilis = 1 x 103 to 1 x 106 CFU/ml and 5 x 107 to 6 x 108 CFU/clot). Conclusion: This standardised and reproducible model of intra-abdominal infection and abscess formation seems well suited for further use and development in experiments on the pathophysiology of intra-abdominal infection and abscesses.