Clostridium bacteria, computer illustration. Clostridia are spore-forming bacteria that include several human pathogenic species, C. difficile, C. tetani, C. botulinum, C. perfringens, and others. 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. C. tetani is the causative agent of tetanus, C. botulinum causes food poisoning botulism, C. perfringens causes gas gangrene and also food poisoning. Clostridium novyi (oedematiens) causes gas gangrene and infectious necrotic hepatitis. The toxins produced by C. tetani (tetanospasmin) and C. botulinum are among the most dangerous known. Some of the clostridia species are involved in the development of bacterial vaginosis.