Fatal pseudomembranous colitis associated with a variant clostridium difficile strain not detected by toxin A immunoassay.
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.
Johnson
S
S
Medical Service, Veterans Affairs Chicago Health Care System-Lakeside, 333 East Huron Street, Chicago, IL 60611, USA.
Kent
S A
SA
O'Leary
K J
KJ
Merrigan
M M
MM
Sambol
S P
SP
Peterson
L R
LR
Gerding
D N
DN
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
D001428:Bacterial Vaccines