I believe that you are referring to: C. difficile.
"C. difficile is the most serious cause of antibiotic-associated diarrhea (AAD)" hence the Frencg Difficile -difficult. Full article here: http://en.wikipedia.org/wiki/Clostridium_difficile
Clostridium difficile (C. difficile) is a type of bacteria that can cause symptoms ranging from diarrhea to life-threatening inflammation of the colon. It is often associated with healthcare settings and can be transmitted through spores on surfaces or through fecal-oral contact. Treatment typically involves antibiotics targeted at the bacteria.
what is cedeficil