In 1861, when Louis Pasteur described the first spore-forming anaerobic bacterium, it was still called Bacillus, in contrast to the non-spore-forming Bacteria. However, by 1923 in his first edition of the Manual of Determinative Bacteriology, David H. Bergey described the anaerobic spore formers as Clostridium (Seifert, 1995).

Clostridia are Gram-positive obligate anaerobic rods with a reservoir in soil, water, sewage, decaying vegetation, animal and plant products and in the intestinal tract of humans and animals. Although Clostridium spp. are classed as anaerobic, some species can grow in the presence of oxygen but do not form spores under these conditions (Seifert, 1995). Clostridium spp. differ from other spore formers not only in being anaerobes, but also in lacking catalase and not reducing sulfate (Seifert, 1995).