MICROBIOLOGY

• Spore-forming anaerobe, Gram-positive bacillus [Fig 1].
  
  • Found in human and animal feces, also in water and soils.
  • Reclassified as molecular sequencing suggests that the organism should be in the Peptostreptococcaceae family and termed Peptoclostridium.
    • Clostridioides difficile name was selected to differentiate from Clostridiaspp., which are not related but allow for less clinical confusion moving from the long-standing terminology of Clostridium difficile[18].
• Produces toxins A and B that cause colitis in humans.
• Occasionally grown in anaerobic cultures, rarely a cause of infection other than colitis.
• Resistance described to metronidazole and high MICs correlates with poorer outcomes[8].
  • Increased MICs to vancomycin and fidaxomicin were also seen in some isolates rarely, but the clinical significance is not certain[7].