Clostridium difficile, commonly known as C.diff., is recognized as one of the most important and debilitating causes of diarrhea and intestinal upset in the US. C. diff. is sometimes found in small numbers among the normal intestinal flora of humans, but it is now believed that the use (and overuse) of antibiotics creates conditions which allow C.diff. to become an opportunistic infection.
C.diff reproduces by binary fission, like most bacteria do. Since this is an exponential process, the population of bacteria can increase very rapidly when conditions are favorable. It can also form resistant spores to survive unfavorable conditions.
C.diff. produces two exotoxins, which have been named TcdA and TcdB. Both toxins are similar in structure and activity, and both cause apoptosis of cells in the lining of the large intestine.