Mortality in Murine Peritonitis Correlates with Increased Escherichia coli Adherence to the Intestinal Mucosa

Abstract

During peritonitis, bacterial adherence is the initial step in a series of events that include mucosal infection, bacterial translocation, organ dysfunction, and death. Adherent Escherichia coli levels increase in response to stress. This study was designed to assess the adherence of E. coli to the cecal mucosa after cecal ligation and puncture (CLP) of increasing severity and to determine whether a relationship exists between adherence of bacteria and mortality. Sham surgery, sterile peritonitis (thioglycollate administration), lethal CLP (18-gauge double-puncture), and nonlethal CLP (23-gauge single-puncture) were performed on Swiss Webster mice and compared with normal mice or before CLP (time 0). Specimens of bowel tissue were harvested, and serial log dilutions of homogenized specimens or bowel contents were plated and cultured on media selective for determination of individual bacterial species. Low levels of E. coli and Proteus mirabilis adhered to the mucosa of unmanipulated controls; however, adherence of both species increased significantly by 18 hours after both lethal and nonlethal CLP. After 18 hours, adherent E. coli levels increased by greater than 5 x 106-fold compared to unmanipulated controls, whereas P. mirabilis levels decreased. After nonlethal CLP, adherent P. mirabilis increased 3 x 106-fold compared to unmanipulated animals, whereas E. coli levels did not increase after 24 hours. Sterile peritonitis had little effect on bacterial adherence. Higher levels of adherent E. coli in the cecum correlate with the increased mortality observed after lethal CLP. Higher levels of adherent P. mirabilis appear to prevent the overgrowth of adherent E. coli following nonlethal CLP. Our data indicate that E. coli plays a key role in mortality from polymicrobial peritonitis and that Proteus may be antagonistic to E. coli in murine peritonitis.