Effects of laparoscopic models on anaerobic bacterial growth with bacteroides fragilis in experimentally induced peritonitis.

Background: Previous reports of recurrent intra-abdominal abcess formation after the laparoscopic treatment of perforated acute appendicitis led us to investigate the possible effects of gas insufflation on the spread of infection. We previously showed that Escherichia coli counts were significantly higher in a laparoscopy group that underwent carbon dioxide (CO2) insufflation than in control and laparotomy groups. The aim of this study is to investigate the effects of intra-abdominal CO2 and nitrous oxide (N2O) insufflation on anaerobic bacterial growth in a rat model.

Methods: A standard strain of Bacteroides fragilis (ATCC 25285) was injected intraperitoneally (1 x 10(6) cfu/mL per kilogram) in 40 Wistar rats under sterile conditions. Forty rats with induced peritonitis were randomly divided into five groups: control, laparotomy, CO2 insufflation, N2O insufflation, and one group without pneumoperitoneum. Eight hours after the intraperitoneal injection of B. fragilis, peritoneal aspirates were obtained and inoculated onto Brucella agar. At the sixteenth hour of induced peritoneal infection (corresponding to hour 8 in the laparoscopy groups) all animals underwent laparotomy; peritoneal aspirates were obtained and inoculated into Brucella agar for bacterial counts. The colonies of B. fragilis were counted manually, and the results were expressed as the mean number of colony-forming units per milliliter.

Results: No significant differences in microorganism counts were noted between the study groups before the procedure (p>.05 for all comparisons). We observed a significant increase in the number of bacteria (mean +/- SD) in the CO2 insufflation group between hour 8 and hour 16 of peritoneal contamination.

Conclusion: The results suggest that CO2 insufflation may promote the growth of intra-abdominal anaerobic bacteria. Such bacterial growth may lead to intra-abdominal abcess formation or cause localized peritonitis to develop into generalized peritonitis. We suggest that laparoscopy without pneumoperitoneum may be preferred in patients with peritonitis.