Bacteria, toxins, and the peritoneum.

Intraperitoneal infections are caused by members of the gastrointestinal flora, mainly Escherichia coli, enterococci, Klebsiella, Enterobacter, Proteus, Bacteroides, anaerobic cocci, Clostridia, and Fusobacteria. The Gram-negative aerobic bacteria exert their pathogenic potential mainly through endotoxin which acts by way of mediators, causing systemic septic response and, initially, the local response of the peritoneal cavity. The main virulence factors of anaerobic bacteria are exoenzymes and capsular polysaccharides. Peritoneal infections are truly synergistic infections. The most important synergistic mechanisms are protection against host defense and creation of a suitable environment by one member of the flora for another. Aside from bacteria, certain adjuvant substances, i.e., bile, gastric juice, blood, and necrotic tissue, play a role in the pathogenesis of peritonitis. The peritoneum deals with an infection in 3 ways: first, the direct absorption of bacteria into the lymphatics via the stoma of the diaphragmatic peritoneum; second, the local destruction of bacteria through phagocytosis by either resident macrophages or polymorphonuclear granulocytes attracted to the peritoneal cavity; and third, the localization of the infection in the form of an abscess.