Comparative genomic analysis of Escherichia coli 0157:H7 isolated from super-shedder and low-shedder cattle
Munns, Krysty D.
Laing, Chad R.
Gannon, Victor P. J.
Selinger, L. Brent
McAllister, Tim A.
Public Library of Science
Cattle are the primary reservoir of the foodborne pathogen Escherichia coli O157:H7, with the concentration and frequency of E. coli O157:H7 shedding varying substantially among individual hosts. The term ‘‘super-shedder” has been applied to cattle that shed 104 cfu E. coli O157:H7/g of feces. Super-shedders have been reported to be responsible for the majority of E. coli O157:H7 shed into the environment. The objective of this study was to determine if there are phenotypic and/or genotypic differences between E. coli O157:H7 isolates obtained from super-shedder compared to low-shedder cattle. From a total of 784 isolates, four were selected from low-shedder steers and six isolates from super-shedder steers (4.01–8.45 log cfu/g feces) for whole genome sequencing. Isolates were phage and clade typed, screened for substrate utilization, pH sensitivity, virulence gene profiles and Stx bacteriophage insertion (SBI) sites. A range of 89–2473 total single nucleotide polymorphisms (SNPs) were identified when sequenced strains were compared to E. coli O157:H7 strain Sakai. More non-synonymous SNP mutations were observed in low-shedder isolates. Pan-genomic and SNPs comparisons did not identify genetic segregation between supershedder or low-shedder isolates. All super-shedder isolates and 3 of 4 of low-shedder isolates were typed as phage type 14a, SBI cluster 3 and SNP clade 2. Super-shedder isolates displayed increased utilization of galactitol, thymidine and 3-O-β-D-galactopyranosyl-Darabinose when compared to low-shedder isolates, but no differences in SNPs were observed in genes encoding for proteins involved in the metabolism of these substrates. While genetic traits specific to super-shedder isolates were not identified in this study, differences in the level of gene expression or genes of unknown function may still contribute to some strains of E. coli 0157:H7 reaching high densities within bovine feces.
Sherpa Romeo green journal; open access
Escherichia coli 0157:H7 , E. coli , Super-shedder cattle , Low-shedder cattle , Cattle -- Feces
Munns, K. D., Zaheer, R., Xu, Yohg, Stanford, K., Laing, C. R., Gannon, V. P. J., ... McAllister, T. A. (2016). Comparative genomic analysis of Escherichia coli 0157:H7 isolated from super-shedder and low-shedder cattle. PLoS ONE, 11(3), e0151673. doi:10.1371/journal.pone.0151673