Clostridioides difficile: Characteristics, Disease, Lab Diagnosis

Clostridioides (formerly Clostridium) difficile causes life-threatening diarrhea. Clostridium difficile infection (CDI) is a leading cause of hospital-associated gastrointestinal illness.  This infection mostly occurs in people who have had recent medical care (hospitalized or recently hospitalized patients), or recent antibiotic use, or recent chemotherapy.

Clostridium difficile
Clostridioides difficile


  1. Clostridioides difficile is a major nosocomial enteric pathogen in hospitals.
  2. It is an anaerobic, Gram-positive rod.
  3. It is a sporeforming rod that readily survives on fomites (inanimate objects) such as floors, bed rails, call buttons, doorknobs, hands of hospital personnel.
  4. New strains of Clostridioides difficile with increased virulence and fluoroquinolone resistance are a major concern.

In hospitals, the transmission of Clostridioides difficile occurs via the hands of health-care workers, direct exposure to contaminated patient-care items (e.g., rectal thermometers), and high-touch surfaces in patients’ bathrooms (e.g., doorknobs).


  • Toxin A: enterotoxin damaging mucosa leading to fluid increase; granulocyte attractant
  • Toxin B: cytotoxin: cytopathic

Disease(s): antibiotic-associated (clindamycin, cephalosporins, arnoxicillin, arnpicillin) diarrhea, colitis, or pseudomembranous colitis (yellow plaques on colon)

Pseudomembranous Colitis (PMC)

  1. Inflammatory disease of the large bowel
  2. Caused by toxins of anaerobic organisms Clostridioides difficile and occasionally by other Clostridia and also Staphylococcus aureus.
  3. Normal condition: Clostridioides difficile usually acquired from the hospital environment is suppressed by normal flora.
  4. Almost every antimicrobial agent and several cancer agents have been associated with the development of pseudomembranous colitis.
Spread of Clostridium difficile and how to prevent it (Image source CDC)
Spread of Clostridioides difficile and how to prevent it (Image source CDC)
Impact and Risk of C.difficile infections (image source: CDC)
Impact and Risk of Clostridioides difficile infections
(image source: CDC)

Laboratory diagnosis of Clostridioides difficile Infections (CDI)

Glutamate dehydrogenase (GDH) antigen test or toxin A/B test are currently in use for the diagnosis of Clostridioides difficile infections. GDH antigen is produced by all Clostridioides difficile, toxins (A and B) produced by some toxigenic strains of Clostridioides difficile.

Stool collection and submission: 

  • Submit fresh liquid stool samples  (i.e. stool conforms to the container) for  suspected CDI
  • Collect specimen in clean, watertight container.
  • Refrigerate (store at 2 – 8°C) until testing can be done.

The current gold standard for Clostridioides difficile toxin testing is a well-performed cell culture cytotoxicity assay but it is not available everywhere.

Interpretation of Clostridioides difficile Assay Results*2:
(Note: Testing algorithm may differ according to hospital protocols)

GDH ResultToxin Assay ResultInterpretationRecommendations
NegativeNegativeNo C. difficile presentNo further action. Repeat testing is discouraged.
PositivePositiveToxigenic C. difficile is presentUtilize contact isolation precautions and begin therapy according to management algorithm. Repeat testing is discouraged.
PositiveNegativeNon-toxigenic C.difficile or false- negative toxin assayDNA confirmatory test for toxin performed. Interpret based on this result
NegativePositiveIndeterminateRepeat test x 1.


  1. Centers for Disease Control and Prevention
  2. Antimicrobial and Clinical Microbiology Guidebook,2010, Nebraska Medical Center

Acharya Tankeshwar

Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. As an asst. professor, I am teaching microbiology and immunology to medical and nursing students at PAHS, Nepal. I have been working as a microbiologist at Patan hospital for more than 10 years.

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