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February 1984

Fibrin in Peritonitis: IV. Synergistic Intraperitoneal Infection Caused by Escherichia coli and Bacteroides fragilis Within Fibrin Clots

Author Affiliations

From the Department of Surgery, University of Minnesota, Minneapolis.

Arch Surg. 1984;119(2):139-144. doi:10.1001/archsurg.1984.01390140005001

• We measured the rate of lethality and abscess formation in rats that underwent intraperitoneal implantation of fibrin clots contaminated with either Escherichia coli or Bacteroides fragilis alone or in combination, to determine whether the two organisms together would produce a synergistic infection. Ten-day mortality produced by 109 colony-forming units (CFU) of E coli was 33.3%. Encapsulated B fragilis led to 3.3% mortality. Escherichia coli (5× 108 CFU) plus B fragilis (5×108 CFU) led to a sharp increase both in the rate and final ten-day mortality (80.0%). Eighty percent of the rats that received E coli (109 CFU within fibrin clots) had abscesses determined on the basis of grossly purulent material. All animals that received B fragilis and survived ten days contained abscesses. Synergy between E coli and B fragilis was noted to occur only when 5 × 108 CFU of each organism was present within the fibrin clot. Lower numbers did not produce significant synergy compared with controls that received either E coli or B fragilis. Quantitation of the number of organisms present at 24 hours within contaminated fibrin clots demonstrated a similar amount of growth of both organisms, either when added alone or in combination as copathogens.

(Arch Surg 1984;119:139-144)