Crohn's bacterial ecosystem identified

Researchers say they now have a better understanding of the so-called microbiome, or bacterial ecosystem, in patients who suffer from Crohn's disease.

In the largest study of its kind, a team of mostly U.S. researchers identified specific bacteria that are abnormally increased or decreased with the onset of the potentially debilitating inflammatory bowel disease.

They took biopsies from 447 individuals with new-onset Crohn's disease and 221 non-affected individuals at multiple sites along the gastrointestinal tract, and then looked for differences between the two groups.

The team found that microbial balance was disrupted in patients who have Crohn's, with beneficial microbes missing and the damaging kind flourishing.

Subjects who had yet to receive any treatment for the disease showed a significant decrease in diversity in the microbial population.

Study may lead to new therapies

One of the author's of the study, Dr. Ramnik Xavier of Massachusetts General Hospital, said the study "forms a blueprint to develop microbial therapeutics."

In addition, the researchers found that biopsies taken from rectal tissue served as good indicators of disease, regardless of where a patient was experiencing inflammation along the gastrointestinal tract. That discovery could lead to doctors relying more on relatively convenient rectal biopsies to reach an early diagnosis.

Scientists have long suspected that an inappropriate response to bacteria in the digestive system somehow causes the immune system to attack the lining of the digestive tract in Crohn's, leading to inflammation.

Prior to a diagnosis, a doctor may prescribe antibiotics, which can help lower the level of bacteria in the intestines and lessen the severity of symptoms.

But the team, which published its study in the March 12 issue of Cell Host & Microbe, found that antibiotics used in children with Crohn's who took part in the study caused a loss of good microbes and an increase in pathological ones.

The study was funded by the Crohn's & Colitis Foundation of America. One in 200 people in the U.S. and Canada are affected by either Crohn's or ulcerative colitis, known collectively as inflammatory bowel disease.

The causes of Crohn's are not well understood, and there is no cure for the illness, known for causing abdominal pain and diarrhea. Patients can take anti-inflammatory drugs (corticosteroids) to manage symptoms.