Clostridioides (ex. Clostridium) difficile

Sean Anderson M. Anderson, M.D., Paul G. Auwaerter, M.D.


  • Spore-forming anaerobe, Gram-positive bacillus [Fig 1].
    • Found in human and animal feces, also in water and soils.
    • Reclassified in 2016 as molecular sequencing suggests that the organism should be in the Peptostreptococcaceae family and termed Peptoclostridium.
      • Clostridioides difficile’s name was selected to differentiate it from Clostridiaspp., which are unrelated but allow for less clinical confusion moving from the long-standing terminology of Clostridium difficile[24].
  • Cycles between a hardy spore (transmissible via fecal-oral route) form and a vegetative (metabolically active) form.
    • Only strains possessing the Pathogenicity Locus (PaLoc) are capable of toxin production.[43]
    • Toxigenic strains can produce toxin A (tcdA) and/or toxin B (tcdB), which causes clinical disease (colitis) when in vegetative form.
    • The presence of secondary bile acids, synthesized by a healthy host microbiome, largely inhibits the germination of C. difficile spores in the colon and thus prevents toxin production and disease[39].
    • Without signals to germinate, spores can latently colonize the colon, though factors contributing to colonization vs clearance remain under studied.
  • Occasionally grown in anaerobic cultures, it is rarely a cause of infection other than colitis.
  • Resistance described to metronidazole and high MICs correlates with poorer outcomes[15].
    • Increased MICs to vancomycin and fidaxomicin have also been documented, and the former may be associated with poorer clinical outcomes[13][5].

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Last updated: May 10, 2024