Surgical manipulation of the intestine results in quantitative and qualitative alterations in luminal Escherichia coli

Abstract

Objectives: To look at the qualitative and quantitative changes in the luminal bacterial flora in response to surgical manipulation of the small intestine. Summary Background Data: The barrier function of the intestine is compromised in pathologic conditions, such as shock, trauma, or surgical stress. Our earlier work has shown that surgical manipulation results in oxidative stress in the intestinal mucosa leading to permeability alterations. Methods: Studies were done on rats, which were randomly divided into four groups (n = 8): group I, control, group II, III, IV different time periods, such as 8, 12, and 24 hours after surgical manipulation, which was simulated by opening the abdominal wall and handling the intestine. The cecal wall and cecal luminal contents were harvested under sterile conditions and processed for quantitation for aerobes and anaerobes. Adherence assays using Hep-2 cells were carried out on Escherichia coli isolated under different experimental conditions. In addition, control E. coli were exposed to superoxide or hydrogen peroxide, followed by subculture and adherence studies. Results: Surgical manipulation of the intestine resulted in qualitative and quantitative alterations in the aerobic bacteria. There was an increase in the number and relative proportion of E. coli in the cecal flora, and there was also an increase in adherence of E. coli to cecal mucosa, which was confirmed by in vitro bacterial adherence studies with HEp-2 cells. These changes were maximum at 12 hours following surgical manipulation and by 24 hours, this came back to control pattern. Control E. coli after in vitro exposure to oxidants also showed increased adherence. Conclusion: These studies suggest that oxidative stress in the mucosa following surgical manipulation results in alterations in the luminal bacteria leading to increased bacterial adherence onto mucosal epithelium, which may contribute to postsurgical complications.