Early portal anaerobic bacteremia in mesenteric ischemia.

The progressive changes in colonic flora and the pattern of bacterial invasion of extracolonic sites were studied in a canine ischemic colon preparation. After 72 hours of colonic ischemia produced by ligation of the common colic and caudal mesenteric arteries, the total number of anaerobic organisms increased, with a concomitant decrease in aerobic organisms within the colon lumen. After 24 hours of ischemia, anaerobic bacteria only appeared in the portal vein and persisted. Aortic blood and peritoneal fluid cultures became positive after 48 hours with the same organisms. Polymicrobial intra-abdominal abscess and systemic Escherichia coli bacteremia occurred only in one animal with necrotic colonic disruption. Acute colonic ischemia promotes an overgrowth of intraluminal anaerobic bacteria, which penetrate the mucosal barrier and progressively invade the portal vein and, later, the systemic circulation.