Researchers at Cedars-Sinai Medical Center in Los Angeles think they may have identified the cause of this mysterious and very common condition, and found an effective way to treat it. The Cedars-Sinai researchers found that 78% of the IBS patients they tested had what they called small intestinal bacterial overgrowth (SIBO), a condition in which excessive amounts of bacteria are present in the small intestine.The researchers treated the patients who tested positive for SIBO with a 10-day course of antibiotics. Tests at the end of that time found that 25 of 47 patients had no bacterial overgrowth present, and that 12 of them had no IBS symptoms, while the symptoms were "significantly reduced" in the other 13. The symptoms were also reduced in the patients in which some SIBO was still detected, suggesting that if treatment had been continued until it was completely eliminated, perhaps with an alternative antibiotic, better results would have been obtained.