Clostridium difficile bacteria, computer illustration. C. difficile is a normal inhabitant of the human intestine, but it can become a pathogen when antibiotics disrupt the normal intestinal flora and allow C. difficile to become established in the colon. A toxin produced by the bacteria can cause diarrhoea, abdominal pain, fever, inflammation of the colon, vomiting and dehydration. Treatment is with antibiotic drugs, although this bacterium has become increasingly resistant to the use of antibiotics.