Mutaflor is a clinically trialed probiotic strain of E.coli for ulcerative colitis.  The clinical evidence is extensive including 3 double blind placebo trials showing equivalency to  the standard of care, 5-ASAs, for maintenance of remission of UC.

“Escherichia coli Nissle is an effective alternative to 5-ASA for maintenance of remission of Ulcerative colitis” -– Journal of Crohns and Colitis (2008)2, 24-62

Efficacy and Indications:
http://mutaflor.ca/health-care-professionals/mutaflor-efficacy/

Listing of clinical trials:
http://mutaflor.ca/health-care-professionals/mutaflor-clinical-studies/