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Journal of Clinical Microbiology, June 2000, p. 2366-2368, Vol. 38, No. 6
Central Public Health Laboratory, Ministry of
Health, Toronto, Ontario M9P 3T1,1 and
Bureau of Microbiology, Canadian Science Centre for Human and
Animal Health, Winnipeg, Manitoba R3E 3R2,2
Canada
Received 30 November 1999/Returned for modification 15 January
2000/Accepted 13 March 2000
Phage typing and DNA macrorestriction fragment analysis by
pulsed-field gel electrophoresis (PFGE) were evaluated for use in the
epidemiological subtyping of Escherichia coli serogroup O157 strains isolated in Ontario, Canada. Among 30 strains isolated from patients with sporadic cases of infection, 22 distinct
XbaI macrorestriction patterns were identified and 17 strains exhibited unique PFGE patterns. In contrast, phage typing
identified only seven different phage types and 17 strains belonged to
the same phage type. A total of 25 phage type-macrorestriction pattern combinations were identified among the strains from patients with sporadic cases of infection. PFGE subtyping differentiated between unrelated strains that exhibited the same phage type, and in one group
of strains, phage typing differentiated between strains of the same
PFGE subtype. Both typing procedures correctly identified outbreak-related isolates as belonging to the same type in four separate outbreaks. Each outbreak strain was characterized by a
distinct macrorestriction pattern, while phage typing subdivided the
outbreak strains into only three different types. A small percentage of
outbreak-related isolates had PFGE patterns that differed slightly (one
or two DNA fragment differences) from that of the outbreak strain. On
the other hand, each isolate from the same outbreak belonged to the
same phage type as that of the outbreak strain. We conclude that phage
typing and PFGE fingerprinting represent complementary procedures for
the subtyping of E. coli serogroup O157 and that the
combined use of these procedures provides optimal discrimination.
0095-1137/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Epidemiologic Subtyping of Escherichia
coli Serogroup O157 Strains Isolated in Ontario by Phage Typing
and Pulsed-Field Gel Electrophoresis
*
Corresponding author. Mailing address: Standards and
Methods Development Section, Central Public Health Laboratory, 81 Resources Rd., Toronto, Ontario M9P 3T1, Canada. Phone: (416) 235-5709. Fax: (416) 235-5951. E-mail:
martin.preston{at}moh.gov.on.ca.
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