Sorry, it stands for "clostridium difficile". This is an opportunistic microorganism that sometimes proliferates in large numbers within the GI tract when Antibiotics are taken causing a very serious form of colitis that can be life-threatening. Basically, antiobiotics kill all denizens of the colon, good and bad. Cdiff is then free to recolonize the area as there is nothing to stop it from spreading (it is normally inhibited by the "good" flora citizens of the bowel).
Just wondered if Lugol's would have the same effect as it is also a broad spectrum microbe killer.