title: Comparison of whole genome sequences from human and non-human Escherichia coli O26 strains.
abstract: Shiga toxin-producing Escherichia coli (STEC) O26 is the second leading E. coli serogroup responsible for human illness outbreaks behind E. coli O157:H7. Recent outbreaks have been linked to emerging pathogenic O26:H11 strains harboring stx 2 only. Cattle have been recognized as an important reservoir of O26 strains harboring stx 1; however the reservoir of these emerging stx 2 strains is unknown. The objective of this study was to identify nucleotide polymorphisms in human and cattle-derived strains in order to compare differences in polymorphism derived genotypes and virulence gene profiles between the two host species. Whole genome sequencing was performed on 182 epidemiologically unrelated O26 strains, including 109 human-derived strains and 73 non-human-derived strains. A panel of 289 O26 strains (241 STEC and 48 non-STEC) was subsequently genotyped using a set of 283 polymorphisms identified by whole genome sequencing, resulting in 64 unique genotypes. Phylogenetic analyses identified seven clusters within the O26 strains. The seven clusters did not distinguish between isolates originating from humans or cattle; however, clusters did correspond with particular virulence gene profiles. Human and non-human-derived strains harboring stx 1 clustered separately from strains harboring stx 2, strains harboring eae, and non-STEC strains. Strains harboring stx 2 were more closely related to non-STEC strains and strains harboring eae than to strains harboring stx 1. The finding of human and cattle-derived strains with the same polymorphism derived genotypes and similar virulence gene profiles, provides evidence that similar strains are found in cattle and humans and transmission between the two species may occur.
authors: U.S. Meat Animal Research Center, United States Department of Agriculture, Agricultural Research Service Clay Center, NE, USA.
authors: Keri N
authors: KN
authors: Norman
authors: U.S. Meat Animal Research Center, United States Department of Agriculture, Agricultural Research Service Clay Center, NE, USA.
authors: Michael L
authors: ML
authors: Clawson
authors: Division of Foodborne, Waterborne and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention Atlanta, GA, USA.
authors: Nancy A
authors: NA
authors: Strockbine
authors: Western Regional Research Center, United States Department of Agriculture, Agricultural Research Service Albany, CA, USA.
authors: Robert E
authors: RE
authors: Mandrell
authors: Laboratory for Foodborne Zoonoses, Public Health Agency of Canada Guelph, ON, Canada.
authors: Roger
authors: R
authors: Johnson
authors: Laboratory for Foodborne Zoonoses, Public Health Agency of Canada Guelph, ON, Canada.
authors: Kim
authors: K
authors: Ziebell
authors: Division of Animal and Food Microbiology, Center for Veterinary Medicine, Food and Drug Administration Laurel, MD, USA.
authors: Shaohua
authors: S
authors: Zhao
authors: Eastern Regional Research Center, United States Department of Agriculture, Agricultural Research Service Wyndmoor, PA, USA.
authors: Pina M
authors: PM
authors: Fratamico
authors: Food and Environment Research Agency Sand Hutton, York, UK.
authors: Robert
authors: R
authors: Stones
authors: Division of Microbiology, Center for Food Safety and Applied Nutrition, Office of Regulatory Science, Food and Drug Administration College Park, MD, USA.
authors: Marc W
authors: MW
authors: Allard
authors: U.S. Meat Animal Research Center, United States Department of Agriculture, Agricultural Research Service Clay Center, NE, USA.
authors: James L
authors: JL
authors: Bono
mesh_terms: D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D004926:Escherichia coli / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology* / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics; D016680:Genome, Bacterial; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D054323:Shiga-Toxigenic Escherichia coli / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D037521:Virulence Factors / Q000235:genetics
chemical_list: D029968:Escherichia coli Proteins; D037521:Virulence Factors
keywords: Escherichia coli; O26; Shiga toxins; phylogenetic; polymorphisms