I firmly believe that my IBS began when I was on tetracycline and simultaneously was infected from bacteria from water I drank from a mountain spring. I think the tetracycline obliterated the "good" bacteria in my bowel, so that it couldn't fight off the other bacteria. Before the tetracycline, I was always able to fight off viruses or infectons and return to normal. Two doctors have concurred with this opinion. From now on, I won't take any tetracycline, or other strong antibiotic, unless it's a life-threatening condition. I only wish I would have known then what I know now!