The microbiology of postoperative peritonitis.

Postoperative peritonitis carries a higher risk of complications and mortality than does community-acquired disease. Little, however, is known about the specific microbiology of this condition. To gain insight into this problem, the microbiological findings of 67 patients with postoperative peritonitis were compared with those of 68 patients with community-acquired peritonitis. In a comparison of postoperative peritonitis with community-acquired disease, the number of isolates of enterococci (23 versus 6) and Enterobacter species (13 versus 4) were increased and the number of isolates of Escherichia coli (21 versus 42) were reduced. Antibiotic therapy before reintervention increased the number of resistant organisms at relaparotomy (33% versus 8%). The in vitro efficacy of the primary antibiotic or combination of drugs did not affect mortality rates (40% versus 38% after effective and ineffective treatment, respectively). Thus, the microbiology of postoperative peritonitis differs significantly from that of community-acquired disease, and specific antibiotic therapy is required, despite the doubtful impact on survival.