Scientists have long puzzled over why "bad" bacteria such as E. coli can thrive in the guts of those with inflammatory bowel disease (IBD), causing serious diarrhea. Now UC Davis researchers have discovered the answer-one that may be the first step toward finding new and better treatments for IBD.
The researchers discovered a biological mechanism by which harmful bacteria grow, edge out beneficial bacteria and damage the gut in IBD. This new understanding, published in the Feb. 8 issue of Science, may help researchers develop new treatments for IBD with fewer side effects than current therapies.
IBD begins when "good" bacteria are mistakenly killed by the immune system, while harmful bacteria multiply - resulting in inflammation and damage to the intestines, and chronic episodes of abdominal pain, cramping, diarrhea and other changes in bowel habits. It's estimated that IBD, which includes ulcerative colitis and Crohn's disease, affects 1.4 million people in the U.S., according to the Centers for Disease Control and Prevention.
In test-tube and animal studies, the researchers found that potentially harmful bacteria in the intestine called Enterobacteriaceae use nitrate - a byproduct formed during the intestinal inflammation in IBD - to grow and thrive. Enterobacteriaceae strains include certain E. coli bacteria, which can worsen the intestinal damage of IBD. Eventually, the intestines of those with IBD become overrun by harmful bacteria, and the numbers of normal good bacteria in the gut decrease.
"Much like humans use oxygen, E. coli can use nitrate as a replacement for oxygen to respire, produce energy and grow," said lead author Andreas Baumler, a professor of medical microbiology and immunology at UC Davis.
"In IBD, nitrate produced by inflammation in the gut allows E. coli to take a deep 'breath,' and beat out our beneficial microbes in the competition for nutrients," he said.