title: Fatal pseudomembranous colitis associated with a variant clostridium difficile strain not detected by toxin A immunoassay.
abstract: 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.
  
  
  METHODS
  Case report, molecular investigation, and laboratory survey.
  
  
  METHODS
  Tertiary care hospital in Chicago, Illinois.
  
  
  METHODS
  An 86-year-old man.
  
  
  METHODS
  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.
authors.affiliation: Medical Service, Veterans Affairs Chicago Health Care System-Lakeside, 333 East Huron Street, Chicago, IL 60611, USA.
authors.forename: S
authors.initials: S
authors.lastname: Johnson
authors.forename: S A
authors.initials: SA
authors.lastname: Kent
authors.forename: K J
authors.initials: KJ
authors.lastname: O'Leary
authors.forename: M M
authors.initials: MM
authors.lastname: Merrigan
authors.forename: S P
authors.initials: SP
authors.lastname: Sambol
authors.forename: L R
authors.initials: LR
authors.lastname: Peterson
authors.forename: D N
authors.initials: DN
authors.lastname: Gerding
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001428:Bacterial Vaccines / Q000032:analysis; D016360:Clostridioides difficile / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D004761:Enterocolitis, Pseudomembranous / Q000175:diagnosis / Q000382:microbiology*; D017809:Fatal Outcome; D006801:Humans; D007118:Immunoassay / Q000379:methods; D008297:Male
chemical_list: D001428:Bacterial Vaccines