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Comparison of whole genome sequences from human and non-human Escherichia coli O26 strains.

Norman KN, Clawson ML, Strockbine NA, Mandrell RE, Johnson R, Ziebell K, Zhao S, Fratamico PM, Stones R, Allard MW, Bono JL - Front Cell Infect Microbiol (2015)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: U.S. Meat Animal Research Center, United States Department of Agriculture, Agricultural Research Service Clay Center, NE, USA.

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.

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Virulence gene profiles within the 64 polymorphism-derived genotypes. Each bar or stacked bar represents the number of strains with the virulence gene profile per genotype.
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Figure 2: Virulence gene profiles within the 64 polymorphism-derived genotypes. Each bar or stacked bar represents the number of strains with the virulence gene profile per genotype.

Mentions: The genotypes of 289 O26 strains (241 STEC and 48 non-STEC) were concatenated from 283 validated polymorphisms and yielded 64 unique polymorphism-derived genotypes (Supplemental Table 3). The 64 genotypes could be derived from a minimal set of 43 polymorphisms (Supplemental Table 4). From these, 24 genotypes were exclusively found in human-isolated strains, 19 exclusively from the non-human sources, and 21 were found in both human and non-human strains (Figure 1, Supplemental Table 1). Genotypes 14 and 25 had the highest frequency (21 strains) of STEC O26 human strains while genotype 32 had the highest frequency (nine strains) of STEC O26 non-human strains. The 15-stx2 only strains were placed in six genotypes (1, 34, 43, 46, 47, and 61) and were the exclusive stx profile in three of those genotypes (1, 46, and 47) (Supplemental Table 1). Of the strains that carried stx2 only, 66.7% fell within genotype 47 (Figure 2). The 210-stx1 only strains were placed in 39 different genotypes with the highest frequency (22 strains) in genotype 25 followed by genotypes 21 and 27 (21 strains each). The 18 strains with both stx1 and stx2 strains were placed in eight different genotypes with the highest frequency (six strains) in genotype 14. Genotypes 14 and 25 had the highest frequency (23 strains) of US strains while genotype 21 had the highest frequency (nine strains) of Canadian strains. The 48 non-STEC strains were placed in 24 different genotypes with the highest frequency (10 strains) in genotype 63 followed by genotype 57 (six strains).


Comparison of whole genome sequences from human and non-human Escherichia coli O26 strains.

Norman KN, Clawson ML, Strockbine NA, Mandrell RE, Johnson R, Ziebell K, Zhao S, Fratamico PM, Stones R, Allard MW, Bono JL - Front Cell Infect Microbiol (2015)

Virulence gene profiles within the 64 polymorphism-derived genotypes. Each bar or stacked bar represents the number of strains with the virulence gene profile per genotype.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4356229&req=5

Figure 2: Virulence gene profiles within the 64 polymorphism-derived genotypes. Each bar or stacked bar represents the number of strains with the virulence gene profile per genotype.
Mentions: The genotypes of 289 O26 strains (241 STEC and 48 non-STEC) were concatenated from 283 validated polymorphisms and yielded 64 unique polymorphism-derived genotypes (Supplemental Table 3). The 64 genotypes could be derived from a minimal set of 43 polymorphisms (Supplemental Table 4). From these, 24 genotypes were exclusively found in human-isolated strains, 19 exclusively from the non-human sources, and 21 were found in both human and non-human strains (Figure 1, Supplemental Table 1). Genotypes 14 and 25 had the highest frequency (21 strains) of STEC O26 human strains while genotype 32 had the highest frequency (nine strains) of STEC O26 non-human strains. The 15-stx2 only strains were placed in six genotypes (1, 34, 43, 46, 47, and 61) and were the exclusive stx profile in three of those genotypes (1, 46, and 47) (Supplemental Table 1). Of the strains that carried stx2 only, 66.7% fell within genotype 47 (Figure 2). The 210-stx1 only strains were placed in 39 different genotypes with the highest frequency (22 strains) in genotype 25 followed by genotypes 21 and 27 (21 strains each). The 18 strains with both stx1 and stx2 strains were placed in eight different genotypes with the highest frequency (six strains) in genotype 14. Genotypes 14 and 25 had the highest frequency (23 strains) of US strains while genotype 21 had the highest frequency (nine strains) of Canadian strains. The 48 non-STEC strains were placed in 24 different genotypes with the highest frequency (10 strains) in genotype 63 followed by genotype 57 (six strains).

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: U.S. Meat Animal Research Center, United States Department of Agriculture, Agricultural Research Service Clay Center, NE, USA.

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.

Show MeSH
Related in: MedlinePlus