Clostridioides difficile

Clostridioides difficile
C. difficile colonies on a blood agar plate
Electron micrograph of the bacterium
Scientific classification
Domain:	Bacteria
Phylum:	Bacillota
Class:	Clostridia
Order:	Eubacteriales
Family:	Peptostreptococcaceae
Genus:	Clostridioides
Species:	C. difficile
Binomial name
Clostridioides difficile (Hall & O'Toole, 1935) Lawson & Rainey, 2016
Synonyms
Bacillus difficilis Hall & O'Toole, 1935[1] Clostridium difficile (Hall & O'Toole, 1935) Prévot, 1938[2] Peptoclostridium difficile [3]

Clostridioides difficile (syn. Clostridium difficile) is a bacterium known for causing serious diarrheal infections, and may also cause colon cancer.^[4][5] It is known also as C. difficile, or C. diff (/siː dɪf/), and is a Gram-positive species of spore-forming bacteria.^[6] Clostridioides spp. are anaerobic, motile bacteria, ubiquitous in nature and especially prevalent in soil. Its vegetative cells are rod-shaped, pleomorphic, and occur in pairs or short chains. Under the microscope, they appear as long, irregular (often drumstick- or spindle-shaped) cells with a bulge at their terminal ends (forms subterminal spores). Under Gram staining, C. difficile cells are Gram-positive and show optimum growth on blood agar at human body temperatures in the absence of oxygen. C. difficile is catalase- and superoxide dismutase-negative, and produces up to three types of toxins: enterotoxin A, cytotoxin B and Clostridioides difficile transferase.^[7] Under stress conditions, the bacteria produce spores that are able to tolerate extreme conditions that the active bacteria cannot tolerate.^[8]

Clostridioides difficile is an important emerging human pathogen; according to the CDC, in 2017 there were 223,900 cases in hospitalized patients and 12,800 deaths in the United States.^[9] Although C. difficile is commonly known as a hospital and antibiotic associated pathogen, at most one third of infections can be traced to transmission from an infected person in hospitals,^[10] and only a small number of antibiotics are directly associated with an elevated risk of developing a C. difficile infection (CDI), namely vancomycin, clindamycin, fluoroquinolones and cephalosporins.^[11][12][13] The majority of infections are acquired outside of hospitals, and most antibiotics have similar elevated risk of infection on par with many non-antibiotic risk factors, such as using stool softeners and receiving an enema.^[14]

Clostridioides difficile can also become established in the human colon without causing disease.^[15] Although early estimates indicated that C. difficile was present in 2–5% of the adult population,^[8] more recent research indicates colonization is closely associated with a history of unrelated diarrheal illnesses, such as food poisoning or laxative abuse.^[16] Individuals with no history of gastrointestinal disturbances appear unlikely to become asymptomatic carriers. These carriers are thought to be a major reservoir of infection.^[17]