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

Objective: To develop a standardised and reproducible model of intra-abdomi nal 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 con centrations of Escherichia coli (E. coli) and Bacteroides fragilis (B. frag ilis) incorporated in fibrin clots (E. coli: 1 x 10(5) colony forming units (CFU) /ml or 1 x 10(8) CFU/ml, B. fragilis: 1 x 10(8) CFU/ml). Four rats w ith fibrin clots without bacteria served as uninfected controls. Main outcome measurements: Macroscopy and bacterial counts in peritoneal fl uid, 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 perit oneal fluid and fibrin clots showed persistently high numbers of E. coli an d B. fragilis for at least 7 days (E. coli = 2 x 10(3) to 1 x 10(6) CFU/ml and 5 x 10(7) to 9 x 10(8) CFU/clot; B. fragilis = 1 x 10(3) to 1 x 10(6) C FU/ml and 5 x 10(7) to 6 x 10(8) CFU/clot). Conclusion: This standardised and reproducible model of intra-abdominal inf ection and abscess formation seems well suited for further use and developm ent in experiments on the pathophysiology of intra-abdominal infection and abscesses.