I concur with the SB Floractiv recommendation, but in combination with other things.

My naturopath put me on this so my body could cope with all the antibiotics I needed when my immune system was trashed after chemo. She said SB Floractiv in the morning & at lunch (this knocks out the unhealthy lifeforms in your gut - "Weed"), then a prebiotic powder (this "feeds" the good guys), then finally the Inner health plus at the end of the day (adds in the bacteria that you want - "seed"). It worked really well.