LOS ANGELES—An overgrowth of bacteria in the gut has been definitively linked to irritable bowel syndrome, in the results of a new Cedars-Sinai study which used cultures from the small intestine. This is the first study to use this “gold standard" method of connecting bacteria to the cause of the disease that affects an estimated 30 million people in the United States.
Previous studies have indicated that bacteria play a role in the disease, including breath tests detecting methane—a byproduct of bacterial fermentation in the gut. This study was the first to make the link using bacterial cultures.
The study, in the current issue of Digestive Diseases and Sciences, examined samples of patients’ small bowel cultures to confirm the presence of small intestinal bacterial overgrowth—or SIBO—in more than 320 subjects. In patients with IBS, more than a third also were diagnosed with small intestine bacterial overgrowth, compared to fewer than 10 percent of those without the disorder. Of those with diarrhea-predominant IBS, 60 percent also had bacterial overgrowth.
“While we found compelling evidence in the past that bacterial overgrowth is a contributing cause of IBS, making this link through bacterial cultures is the gold standard of diagnosis," said Mark Pimentel, MD, director of the Cedars-Sinai GI Motility Program and an author of the study. “This clear evidence of the role bacteria play in the disease underscores our clinical trial findings, which show that antibiotics are a successful treatment for IBS."