Clostridium consists of around 100 species that include common free-living bacteria as well as important pathogens There are five main species responsible for disease in humans.
- C. perfringens: gas gangrene; food poisoning
- C. tetani: tetanus
- C. botulinum: botulism
- C. difficile: pseudomembranous colitis
- C.Sordellii : can cause a fatal infection in exceptionally rare cases after medical abortions