Fatal pseudomembranous colitis associated with a variant Clostridium difficile strain not detected by toxin A immunoassay

S. Johnson*, S. A. Kent, Kevin John O'Leary, M. M. Merrigan, S. P. Sambol, L. R. Peterson, D. N. Gerding

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

111 Scopus citations


Background: Many clinical laboratories use toxin A immuno-assays to test for Clostridiurn 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.

Original languageEnglish (US)
Pages (from-to)434-438
Number of pages5
JournalAnnals of internal medicine
Issue number6
StatePublished - Sep 18 2001

ASJC Scopus subject areas

  • Internal Medicine


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