According to this a company in Germany held the trade mark for it in the US. According to this it would be an "uphill battle" for another company to acquire rights to the Mutaflor at this point.

I'm assuming no one has actually bothered to fund studies of it in the US given that it is unlikely to be a profitable endeavor. Disregarding various historic accounts of its use as a treatment for CDI and testimonies/reviews of individuals professing its effectiveness there is not a lot in the way of studies supporting its use for treatment of CDI.

As I understand the strain of E.Coli in Muraflor is extremely invasive when compared to other pro-biotic bacteria. Alternatives such as VSL3 are comprised of a large variety of less potent bacteria which perhaps might be less effective against CDI. However, I have read that symbioflor-2 might be an equally effective alternative.

However, you have certainly exposed a weak point in my argument. If you can find a compelling statement from the FDA about why they banned Mutaflor, I would definitely award you a delta. However, while the particular example I used might have been weak it still doesn't show that the FDA didn't ban countless other drugs in order to justify additional trials which in turn can be used to justify a larger budget to congress.