Clostridium difficile: Characteristics, Disease and Laboratory Diagnosis

Clostridium difficile (C. difficile) causes life-threatening diarrhea. Clostridium 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
Clostridium difficile


  1. Clostiridum difficle 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 Clostridium difficile with increased virulence and fluoroquinolone resistance is a major concern.

In hospitals the transmission of C.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 Clostridium difficle and occasionally by other Clostridia and also Staphylococcus aureus.
  3. Normal condition: Clostridium difficle 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 Clostridium difficile and how to prevent it (Image source CDC)


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


Laboratory diagnosis of Clostridium difficile Infections (CDI)

Glutamate dehydrogenase (GDH) antigen Test or Toxin A/B test are currently in use for the diagnosis of Clostridium difficile infections. GDH antigen is produced by all C. difficile, toxins (A and B) produced by some toxigenic strains of C. 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 C. difficile toxin testing is a well-performed cell culture cytotoxicity assay but it is not available everywhere.


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

GDH Result ToxinAssay 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

One thought on “Clostridium difficile: Characteristics, Disease and Laboratory Diagnosis

  1. From the transmission source of clostridium difficile, it can be known that everything is with the risk to transmit such diseases. Thus care should be taken to avoid it. Besides there may be isotope labeling ways developed to replace gold standard for C. difficile toxin testing as the latter is not available everywhere.

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