Clostridia are spore-forming, gram-positive, anaerobic bacilli present widely in dust, soil, and vegetation and as normal flora in mammalian gastrointestinal tracts. Pathogenic species produce tissue-destructive and neural exotoxins that contribute to disease manifestations.
Nearly 100 Clostridium species have been identified, but only 25 to 30 commonly cause human or animal disease.
The pathogenic species produce tissue-destructive and neural exotoxins that are responsible for disease manifestations. Clostridia may become pathogenic when tissue oxygen tension and pH are low. Such an anaerobic environment may develop in ischemic or devitalized tissue, as occurs in primary arterial insufficiency or after severe penetrating or crushing injuries. The deeper and more severe the wound, the more prone the patient is to clostridial infection, especially if there is even minimal contamination by foreign matter.
Clostridial disease can also occur after injection of illicit drugs.
Serious noninfectious disease can occur after ingestion of home-canned foods in which clostridia have produced toxins.