Clostridium

Clostridium contains around 250 species that include common free-living bacteria, as well as important pathogens.[6][7] The main species responsible for disease in humans are:[8]

• Clostridium botulinum can produce botulinum toxin in food or wounds and can cause botulism. This same toxin is known as Botox and is used in cosmetic surgery to paralyze facial muscles to reduce the signs of aging; it also has numerous other therapeutic uses.
• Clostridium perfringens causes a wide range of symptoms, from food poisoning to cellulitis, fasciitis, necrotic enteritis[9] and gas gangrene.[10]
• Clostridium tetani causes tetanus.
• Clostridium sordellii can cause a fatal infection in exceptionally rare cases after medical abortions.[11]

Bacillus and Clostridium are often described as Gram-variable, because they show an increasing number of gram-negative cells as the culture ages.[12]

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:[2]

• Clostridium grows in anaerobic conditions; Bacillus grows in aerobic conditions.
• Clostridium forms bottle-shaped endospores; Bacillus forms oblong endospores.
• Clostridium does not form the enzyme catalase; Bacillus secretes catalase to destroy toxic byproducts of oxygen metabolism.

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.[12]

The Schaeffer-Fulton stain (0.5% malachite green in water) can be used to distinguish endospores of Bacillus and Clostridium from other microorganisms.[13] There is a commercially available polymerase chain reaction (PCR) test kit (Bactotype) for the detection of C. perfringens and other pathogenic bacteria.[14]

In general, the treatment of clostridial infection is high-dose penicillin G, to which the organism has remained susceptible.[15] Clostridium welchii and Clostridium tetani respond to sulfonamides.[16] Clostridia are also susceptible to tetracyclines, carbapenems (imipenem), metronidazole, vancomycin, and chloramphenicol.[17]

The vegetative cells of clostridia are heat-labile and are killed by short heating at temperatures above 72–75 °C. The thermal destruction of Clostridium spores requires higher temperatures (above 121.1 °C, for example in an autoclave) and longer cooking times (20 min, with a few exceptional cases of > 50 min recorded in the literature). Clostridia and Bacilli are quite radiation-resistant, requiring doses of about 30 kGy, which is a serious obstacle to the development of shelf-stable irradiated foods for general use in the retail market.[18] The addition of lysozyme, nitrate, nitrite and propionic acid salts inhibits clostridia in various foods.[19][20][21]

Fructooligosaccharides (fructans) such as inulin, occurring in relatively large amounts in a number of foods such as chicory, garlic, onion, leek, artichoke, and asparagus, have a prebiotic or bifidogenic effect, selectively promoting the growth and metabolism of beneficial bacteria in the colon, such as bifidobacteria and lactobacilli, while inhibiting harmful ones, such as clostridia, fusobacteria, and bacteroides.[22]

In the late 1700s, Germany experienced a number of outbreaks of an illness that seemed connected to eating certain sausages. In 1817, the German neurologist Justinus Kerner detected rod-shaped cells in his investigations into this so-called sausage poisoning. In 1897, the Belgian biology professor Emile van Ermengem published his finding of an endospore-forming organism he isolated from spoiled ham. Biologists classified van Ermengem's discovery along with other known gram-positive spore formers in the genus Bacillus. This classification presented problems, however, because the isolate grew only in anaerobic conditions, but Bacillus grew well in oxygen.[2]

Circa 1880, in the course of studying fermentation and butyric acid synthesis, a scientist surnamed Prazmowski first assigned a binomial name to Clostridium butyricum.[23]^:107–108 The mechanisms of anaerobic respiration were still not yet well elucidated at that time,[23]^:107–108 so taxonomy of anaerobes was still nascent.

In 1924, Ida A. Bengtson separated van Ermengem's microorganisms from the Bacillus group and assigned them to the genus Clostridium. By Bengtson's classification scheme, Clostridium contained all of the anaerobic endospore-forming rod-shaped bacteria, except the genus Desulfotomaculum.[2]

• Clostridium thermocellum can use lignocellulosic waste and generate ethanol, thus making it a possible candidate for use in production of ethanol fuel. It also has no oxygen requirement and is thermophilic, which reduces cooling cost.
• Clostridium acetobutylicum was first used by Chaim Weizmann to produce acetone and biobutanol from starch in 1916 for the production of cordite (smokeless gunpowder).
• Clostridium botulinum produces a potentially lethal neurotoxin used in a diluted form in the drug Botox, which is carefully injected to nerves in the face, which prevents the movement of the expressive muscles of the forehead, to delay the wrinkling effect of aging. It is also used to treat spasmodic torticollis and provides relief for around 12 to 16 weeks.[24]
• Clostridium butyricum MIYAIRI 588 strain is marketed in Japan, Korea, and China for Clostridium difficile prophylaxis due to its reported ability to interfere with the growth of the latter.
• Clostridium histolyticum has been used as a source of the enzyme collagenase, which degrades animal tissue. Clostridium species excrete collagenase to eat through tissue and, thus, help the pathogen spread throughout the body. The medical profession uses collagenase for the same reason in the débridement of infected wounds.[2] Hyaluronidase, deoxyribonuclease, lecithinase, leukocidin, protease, lipase, and hemolysin are also produced by some clostridia that cause gas gangrene.[12][25]
• Clostridium ljungdahlii, recently discovered in commercial chicken wastes, can produce ethanol from single-carbon sources including synthesis gas, a mixture of carbon monoxide and hydrogen, that can be generated from the partial combustion of either fossil fuels or biomass.[26]
• Clostridium butyricum converts glycerol to 1,3-propanediol.[27]
• Genes from Clostridium thermocellum have been inserted into transgenic mice to allow the production of endoglucanase. The experiment was intended to learn more about how the digestive capacity of monogastric animals could be improved.
• Nonpathogenic strains of Clostridium may help in the treatment of diseases such as cancer. Research shows that Clostridium can selectively target cancer cells. Some strains can enter and replicate within solid tumors. Clostridium could, therefore, be used to deliver therapeutic proteins to tumours. This use of Clostridium has been demonstrated in a variety of preclinical models.[28]
• Mixtures of Clostridium species, such as Clostridium beijerinckii, Clostridium butyricum, and species from other genera have been shown to produce biohydrogen from yeast waste.[29]

• Clostridium genomes and related information at PATRIC, a Bioinformatics Resource Center funded by NIAID
• Todar's Online Textbook of Bacteriology
• UK Clostridium difficile Support Group
• Pathema-Clostridium Resource
• Water analysis: Clostridium video