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Journal of Clinical Microbiology, March 1998, p. 727-733, Vol. 36, No. 3
Food Research
Institute1 and
Department of Food
Science,4 University of Wisconsin, Madison,
Wisconsin 53706;
Centre for Food and Animal Research,
Agriculture and Agri-Food Canada, Ottawa, Ontario K1A
OC62; and
Department of Health and
Family Services, Wisconsin Division of Health, Bureau of Public
Health, Madison, Wisconsin 537033
Received 15 September 1997/Returned for modification 10 November
1997/Accepted 4 December 1997
Contour-clamped homogeneous electric field pulsed-field gel
electrophoresis (CHEF-PFGE) was used to compare Wisconsin isolates of
Escherichia coli O157:H7, including 39 isolates from a 1994 day care center outbreak, 28 isolates from 18 individuals from the
surrounding geographic area with sporadic cases occurring during the 3 months before the outbreak, and 3 isolates, collected in 1995, from
patients with hemolytic-uremic syndrome (HUS) who were from eastern
Wisconsin counties other than those inhabited by the day care center
and sporadic-case individuals. The technique of CHEF-PFGE using
XbaI identified seven highly related restriction endonuclease digestion profiles (REDPs) (93 to 98% similarity) among
the 39 day care center isolates and nine XbaI REDPs (63 to
93% similarity) among the 28 isolates from sporadic-case individuals, including REDP 33, which was exhibited by both day care and
sporadic-case isolates. PFGE analyses of sequential E. coli
O157:H7 isolates from symptomatic day care center attendees revealed
that the REDPs of 25 isolates from eight patients were
indistinguishable whereas the REDPs of 2 of 6 isolates from two
patients differed slightly (93 to 95% similarity). The REDPs of the
three isolates from 1995 HUS patients were 78 to 83% similar, with
REDP 26 being exhibited by one HUS-associated isolate and an isolate
from one day care attendee who did not develop HUS. The genes for both
Shiga toxins I and II (stx1 and
stx2, respectively) were detected in all but one isolate (sporadic case), and Shiga toxin production by the day care
center isolates was not significantly different from that of the other
isolates, including the three HUS-associated isolates. Analyses of
E. coli O157:H7 isolates from both the day care center
outbreak and sporadic cases by CHEF-PFGE permitted us to define the
REDP variability of an outbreak and geographic region and demonstrated
that the day care center outbreak and a HUS case in 1995 were caused by
E. coli O157:H7 strains endemic to eastern Wisconsin.
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Genomic Comparisons and Shiga Toxin Production
among Escherichia coli O157:H7 Isolates from a Day Care
Center Outbreak and Sporadic Cases in Southeastern Wisconsin
*
Corresponding author. Mailing address: Food Research
Institute, University of Wisconsin, 1925 Willow Dr., Madison, WI
53706-1187. Phone: (608) 263-6936. Fax: (608) 263-1114. E-mail:
cwkaspar{at}facstaff.wisc.edu.
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