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Published on: December 8, 2014
Fatal pseudomembranous colitis associated with a variant clostridium difficile strain not detected by toxin A
S Johnson1, S A Kent, K J O'Leary
1Medical Service, Veterans Affairs Chicago Health Care System-Lakeside, 333 East Huron Street, Chicago, IL 60611, USA.
Background:
Many clinical laboratories use toxin A immunoassays to test for Clostridium difficile.
Objective:
To describe the clinical course of a patient infected with a toxin variant strain of C. difficile that was not detected by toxin A immunoassay; to genetically characterize this strain; and to estimate the number of laboratories that use only toxin A immunoassays.
Design:
Case report, molecular investigation, and laboratory survey.
Setting:
Tertiary care hospital in Chicago, Illinois.
Patient:
An 86-year-old man.
Measurements:
Restriction endonuclease analysis, polymerase chain reaction, and survey of regional clinical laboratories.
Results:
An elderly hospitalized man died of advanced pseudomembranous colitis. Four stool specimens submitted over a 2-month period had tested negative on toxin A immunoassay, but 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, is closely related to a widely disseminated variant, toxinotype VIII. Toxin A immunoassay was the only test being performed for detection of C. difficile at 31 of 67 (46%) regional clinical laboratories.
Conclusions:
Toxin A variant strains of C. difficile cause serious disease and are undetectable in clinical laboratories that use only toxin A immunoassays for C. difficile testing.
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