Clostridium

Clostridium is a genus of Gram-positive bacteria, which includes several significant human pathogens, including the causative agent of botulism. The genus formerly included an important cause of diarrhea, Clostridioides difficile, which was separated after 16S rRNA analysis. They are obligate anaerobes capable of producing endospores. The normal, reproducing cells of Clostridium, called the vegetative form, are rod-shaped, which gives them their name, from the Greek κλωστήρ or spindle. Clostridium endospores have a distinct bowling pin or bottle shape, distinguishing them from other bacterial endospores, which are usually ovoid in shape. Clostridium species inhabit soils and the intestinal tract of animals, including humans. Clostridium is a normal inhabitant of the healthy lower reproductive tract of women. The gut microbiota of healthy humans contains commensal Clostridium bacteria. Species from Clostridium cluster XIVa and Clostridium cluster IV are important in human guts, but despite the naming, these clusters encompass many bacteria outside the genus Clostridium. Clostridium contains around 100 species that include common free-living bacteria, as well as important pathogens. The main species responsible for disease in humans are: Bacillus and Clostridium are often described as gram-variable, because they show an increasing number of gram-negative cells as the culture ages. Clostridium and Bacillus are both in the phylum Firmicutes, but they are in different classes, orders, and families. Microbiologists distinguish Clostridium from Bacillus by the following features: Clostridium and Desulfotomaculum are both in the class Clostridia and order Clostridiales, and they both produce bottle-shaped endospores, but they are in different families. Clostridium can be distinguished from Desulfotomaculum on the basis of the nutrients each genus uses (the latter requires sulfur). Glycolysis and fermentation of pyruvic acid by Clostridia yield the end products butyric acid, butanol, acetone, isopropanol, and carbon dioxide. The Schaeffer-Fulton stain (0.5% malachite green in water) can be used to distinguish endospores of Bacillus and Clostridium from other microorganisms. There is a commercially available polymerase chain reaction (PCR) test kit (Bactotype) for the detection of C. perfringens and other pathogenic bacteria.