Genotypic Characterization and Prevalence of Virulence Factors among Canadian Escherichia coli O157:H7 Strains

Authors

• Kim Ziebell, Public Health Agency of Canada
• Marina Steele, Public Health Agency of Canada
• Yongxiang Zhang, Public Health Agency of Canada
• Andrew K. Benson, University of Nebraska-LincolnFollow
• Eduardo N. Taboada, Public Health Agency of Canada
• Chad Laing, Public Health Agency of Canada
• Scott McEwen, University of Guelph
• Bruce Ciebin, Hamilton Public Health Laboratory
• Roger Johnson, Public Health Agency of Canada
• Victor Gannon, Public Health Agency of Canada

Document Type

Article

Date of this Version

2008

Citation

Applied and Environmental Microbiology, July 2008, p. 4314–4323 Vol. 74, No. 14

Comments

Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Abstract

In this study, the association between genotypic and selected phenotypic characteristics was examined in a collection of Canadian Escherichia coli O157:H7 strains isolated from humans and cattle in the provinces of Alberta, Ontario, Saskatchewan, and Quebec. In a subset of 69 strains selected on the basis of specific phage types (PTs), a strong correlation between the lineage-specific polymorphism assay (LSPA6) genotype and PT was observed with all strains of PTs 4, 14, 21, 31, 33, and 87 belonging to the LSPA6 lineage I (LSPA6-LI) genotype, while those of PTs 23, 45, 67, and 74 belonged to LSPA6 lineage II (LSPA6-LII) genotypes. This correlation was maintained when additional strains of each PT were tested. E. coli O157:H7 strains with the LSPA6-LI genotype were much more common in the collection than were the LSPA6-LII or lineage I/II (LSPA6-LI/II)-related genotypes (82.6, 11.2, and 5.8%, respectively). Of the strains tested, proportionately more LSPA6-LI than LSPA6-LII genotype strains were isolated from humans (52.7% versus 19.7%) than from cattle (47.8% versus 80.2%). In addition, 96.7% of the LSPA6-LII strains carried the stx2c variant gene, while only 50.0% of LSPA6-LI/II and 2.7% of LSPA6-LI strains carried this gene. LSPA6-LII strains were also significantly more likely to possess the colicin D gene, cda (50.8% versus 23.2%), and have combined resistance to streptomycin, sulfisoxazole, and tetracycline (72.1% versus 0.9%) than were LSPA6-LI strains. The LSPA6 genotype- and PT-related characteristics identified may be important markers of specific ecotypes of E. coli O157:H7 that have unique epidemiological and virulence characteristics.