Clostridioides difficile: Characteristics, Disease and Laboratory Diagnosis

Impact and Risk of C.difficile infections (image source: CDC)

Last updated on January 31st, 2020

Clostridioides (formerly Clostridium) difficile causes life-threatening diarrhea. Clostridioides difficile infection (CDI) is a leading cause of hospital associated gastrointestinal illness.  This infections mostly occur 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  which readily survives on fomites (inanimate objects) such as floors, bed rails, call buttons, door knobs, hands of hospital personnel.
  4. New strains of Clostridioides difficile with increased virulence and fluoroquinolone resistance is 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.,door knobs).


  • 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 agents and several cancer agents have been associated with 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 difficiletoxins (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 Result Toxin Assay Result Interpretation Recommendations
Negative Negative No C. difficile present No further action. Repeat testing is discouraged.
Positive Positive Toxigenic C. difficile is present Utilize contact isolation precautions and begin therapy according to management algorithm. Repeat testing is discouraged.
Positive Negative Non-toxigenic C.difficile or false- negative toxin assay DNA confirmatory test for toxin performed. Interpret based on this result
Negative Positive Indeterminate Repeat test x 1.


  1. Centers for Disease Control and Prevention
  2. Antimicrobial and Clinical Microbiology Guidebook,2010, Nebraska Medical Center
About Acharya Tankeshwar 467 Articles
Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. I am working as an Asst. Professor and Microbiologist at Department of Microbiology and Immunology, Patan Academy of Health Sciences, Nepal. If you want me to write about any posts that you found confusing/difficult, please mention in the comments below.

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