Cheshire, this is exactly what I thought might happen. I explained it in that thread we were having below.
You can try treating it with Vitamin C, powdered form, to bowel tolerance with and between meals. Cheap, easy, and you should feel immediate relief. Just back off if you start to get dio. And black tea is good for this too.
The Vitamin C will kill the newly installed bacteria.
Also useful, Viracin. Spices. Any of the antibacterial herbs.
But Vitamin C is best.
If you have to do Antibiotics , Cipro is the choice, as it is easy on you Large GI bacteria.