Rank: Species
Lineage: Bacteria;Firmicutes;Clostridia;Clostridiales;Peptostreptococcaceae;Clostridioides;Clostridioides difficile
Description: Clostridium. This genus comprises about 150 metabolically diverse species of anaerobes that are ubiquitous in virtually all anoxic habitats where organic compounds are present, including soils, aquatic sediments and the intestinal tracts of animals and humans. Characteristic of clostridia is the shape of their cells that resembles a drumstick or spindle ("kloster" is Greek for "spindle"). This shape is attributed to the presence of endospores that develop under conditions unfavorable for vegetative growth and distend single cells terminally or sub-terminally. The endospores of many species are extremely sturdy and survive extended boiling in water and exposure to air. Spores germinate under conditions favorable for vegetative growth, such as anaerobiosis and presence of organic substrates. From the evolutionary perspective, clostridia are considered to be the most ancient bacteria. It is believed that present day Mollicutes (Eubacteria) have evolved regressively (i.e., by genome reduction) from gram-positive clostridia-like ancestors with a low GC content in DNA. Several species of clostridia (e.g., C. perfringens, C. botulinum, C. tetani) are known opportunistic toxin-producing pathogens in animals and humans. Some species are capable of producing organic solvents (acetone, ethanol, etc,), molecular hydrogen and other useful compounds. There are also species that can fix molecular nitrogen and thus are important participants in biological turnaround of nitrogen compounds in nature.Clostridium difficile. This species is now recognized as the major causative agent of pseudomembranous colitis (inflammation of the colon) and diarrhea that may occur following antibiotic treatment. C. difficile infection represents one of the most common nosocomial (originating in a hospital) infections. This bacterium causes a wide spectrum of disease, ranging from mild, self-limiting diarrhea to serious diarrhea and, in some cases, complications such as pseudomembrane formation, toxic megacolon (dilation of the colon) and peritonitis, which often lead to lethality among patients. The bacteria produce high molecular mass polypeptide cytotoxins, A and B. Some strains produce only one of the toxins, others produce both. Toxin A causes inflammatory reaction involving hypersecretion of fluid and hemorrhagic necrosis through triggering cytokine release by neutrophils. Cytotoxin B depolymerizes actin, the major protein of the cytoskeleton, and thus aids in destruction of tissues. The combined action of the toxins results in necrosis of superficial epithelium and edema (fluidic swelling) in affected areas of intestine. Proliferation of C. difficile is normally prevented by normal intestinal microflora, which is believed to inhibit attachment of the bacterium and its toxins to intestinal walls. Alteration of intestinal microbial balance with antibiotic therapy and increased exposure to the bacterium in a hospital setting allows C. difficile to colonize susceptible individuals. r, it has been shown that subinhibitory concentrations of antibiotics promote increased toxin production by C. difficile.
Reference Material:
https://www.ncbi.nlm.nih.gov/genome/?term=Clostridioides%20difficile
