Researchers form Chicago, Illinois, USA, investigated a case of fatal pseudomembranous colitis associated with a variant Clostridium difficile strain that was not detected by toxin A immunoassay.
They described the clinical course of an 86-year-old man who was infected with the toxin variant C. difficile, and died of advanced pseudomembranous colitis.
|46% of laboratories only use toxin A immunoassays for C. difficile testing.
|Annals of Internal Medicine|
In addition, the team genetically characterized the strain. They also estimated the number of laboratories that use only toxin A immunoassays to test for C. difficile.
Four stool specimens from the patient had been submitted over a 2-month period, and had tested negative on toxin A immunoassay. However, a strain of C. difficile with a 1.8-kb deletion of the toxin A gene was recovered from each specimen.
This strain, identified as restriction endonuclease analysis type CF4, was closely related to a widely disseminated variant, toxinotype VIII.
The researchers found that toxin A immunoassay was the only test being performed for detection of C. difficile at 31 of 67 (46%) regional clinical laboratories.
Dr Stuart Johnson and colleagues, from the Veterans Affairs Chicago Health Care System and the Northwestern University Medical School, concluded that toxin A variant strains of C. difficile cause serious disease. They are undetectable in clinical laboratories that use only toxin A immunoassays for C. difficile testing.