Bacterial Flora of the Human Small Intestine

Abstract

The literature regarding the normal bacterial flora of the human gastrointestinal tract has recently been reviewed by Rosebury¹and Donaldson,²and can be summarized as follows: the stomach or upper small intestine may be sterile or contain a sparse bacterial population; those bacteria found in the upper portion of the gastrointestinal tract are considered to be contaminants from the mouth and respiratory tract, and seldom exceed counts of 10⁵bacteria per milliliter of intestinal content; although bacteria in the terminal ileum are often of the fecal type, about 50% of specimens are sterile; an entirely different situation prevails in the colon which is more stagnant and supports a large and varied bacterial population. <h3>Intestinal Bacteria</h3> Our interest in human small intestinal flora arose from research into the lethal role of intestinal bacteria and their products during intestinal strangulation obstruction.^3,4These studies have been concerned with normal