I feel certain that antibiotics can trigger UC in people who are genetically predisposed. In addition to or because of bacterial changes the intestinal mucosa is damaged, leading to chronic inflammation. I say this due to the fact that I developed UC a few years after treatment with 3 different antibiotics for recurrent tonsillitis in my early twenties. But, as Julee70 writes, it does no good to torture yourself trying to figure out what went wrong to harm your daughter; it's best to focus on controlling her symptoms in the most effective and reasonable way. Keep telling yourself that there are worse ailments/afflictions to cope with than UC, things that blind or paralyze, etc. I know a guy who became ill with Crohn's Disease while in dental school; he got it under control, finished school & training, & went on to a successful professional career. He had ups & downs, including need for surgery at one point, but he overcame the obstacles. Life is a struggle for many people. That's just the way things are, not always what we want for ourselves or our loved ones. / Old Hat (nearly 30 yrs with left-sided UC; currently on 3 Colazal daily; seem to be back in remission)