NEW YORK (Reuters Health) - An abnormally high number of bacteria in the small intestine does not appear to be a major factor affecting the symptoms of irritable bowel syndrome, Swedish researchers report in the medical journal Gut.

Irritable bowel syndrome (IBS), or spastic colon, is a common disorder characterized by abdominal pain, diarrhea, cramping, and constipation. The syndrome is thought to arise from overactivity of the nerves in the intestine that control movement.

"The data do not support an important role for small intestinal bacterial overgrowth, according to commonly used clinical definitions, in IBS," senior investigator Dr. Magnus Simren told Reuters Health.

Simren and colleagues at Sahlgrenska University Hospital, Gothenburg, note that a high rate of bacterial overgrowth has been reported in patients with IBS, but these observations were based on tests that only indirectly measured bacteria levels.

They therefore assessed small intestinal bacterial overgrowth by a direct test - bacterial culture of small-bowel test samples - among 162 patients with IBS and 26 healthy subjects. Cultures revealed the exact same rate of intestinal bacterial overgrowth in both groups, 4 percent.

Signs of intestinal movement abnormalities were seen in 86 percent of patients with overgrowth and in 39 percent of patients without overgrowth. The investigators also observed that movement abnormalities did not reliably predict altered small-bowel bacterial levels.