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Journal of Clinical Microbiology, July 2000, p. 2706-2714, Vol. 38, No. 7
Department of Medical
Microbiology1 and Department of
Medicine,3 University of Manitoba,
Microbiology, St. Boniface General Hospital,2
and Infection Control Health Sciences
Centre,5 Winnipeg, Manitoba, Canada, and
Techlab Inc., Blacksburg, Virginia4
Received 9 February 2000/Returned for modification 7 March
2000/Accepted 29 March 2000
Clostridium difficile-associated diarrhea (CAD) is a
very common nosocomial infection that contributes significantly to
patient morbidity and mortality as well as to the cost of
hospitalization. Previously, strains of toxin A-negative, toxin
B-positive C. difficile were not thought to be associated
with clinically significant disease. This study reports the
characterization of a toxin A-negative, toxin B-positive strain of
C. difficile that was responsible for a recently described
nosocomial outbreak of CAD. Analysis of the seven patient isolates from
the outbreak by pulsed-field gel electrophoresis indicated that this
outbreak was due to transmission of a single strain of C. difficile. Our characterization of this strain (HSC98) has
demonstrated that the toxin A gene lacks 1.8 kb from the carboxy repetitive oligopeptide (CROP) region but apparently has no other major
deletions from other regions of the toxin A or toxin B gene. The
remaining 1.3-kb fragment of the toxin A CROP region from strain HSC98
showed 98% sequence homology with strain 1470, previously reported by
M. Weidmann in 1997 (GenBank accession number Y12616), suggesting that
HSC98 is toxinotype VIII. The HSC98 strain infecting patients involved
in this outbreak produced the full spectrum of clinical illness usually
associated with C. difficile-associated disease. This
pathogenic spectrum was manifest despite the inability of this strain
to alter tight junctions as determined by using in vitro tissue culture
testing, which suggested that no functional toxin A was produced by
this strain.
0095-1137/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Characterization of a Toxin A-Negative, Toxin
B-Positive Strain of Clostridium difficile Responsible for a
Nosocomial Outbreak of Clostridium
difficile-Associated Diarrhea
*
Corresponding author. Mailing address: Microbiology,
St. Boniface General Hospital, 409 Tache Ave., Winnipeg, Manitoba,
Canada R2H 2A6. Phone: (204) 237-2105. Fax: (204) 237-7678. E-mail:
malfa{at}cc.umanitoba.ca.
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