The Normal Flora: Gut

The Stomach

Except for the transient carriage of bacteria in food, the stomach and duodenum are usually sterile as few bacteria survive the effects of gastric acid.
(However, infection with H.pylori is common).

The Small Bowel

The small bowel is colonised by:

The Large Bowel

The large bowel has a rich normal flora:

Bacteroides

E. coli

Adapted from a page on The Normal Flora: Gut.