title: Phylogenetically related Argentinean and Australian Escherichia coli O157 isolates are distinguished by virulence clades and alternative Shiga toxin 1 and 2 prophages.
abstract: Shiga toxigenic Escherichia coli O157 is the leading cause of hemolytic uremic syndrome (HUS) worldwide. The frequencies of stx genotypes and the incidences of O157-related illness and HUS vary significantly between Argentina and Australia. Locus-specific polymorphism analysis revealed that lineage I/II (LI/II) E. coli O157 isolates were most prevalent in Argentina (90%) and Australia (88%). Argentinean LI/II isolates were shown to belong to clades 4 (28%) and 8 (72%), while Australian LI/II isolates were identified as clades 6 (15%), 7 (83%), and 8 (2%). Clade 8 was significantly associated with Shiga toxin bacteriophage insertion (SBI) type stx(2) (locus of insertion, argW) in Argentinean isolates (P < 0.0001). In Argentinean LI/II strains, stx(2) is carried by a prophage inserted at argW, whereas in Australian LI/II strains the argW locus is occupied by the novel stx(1) prophage. In both Argentinean and Australian LI/II strains, stx(2c) is almost exclusively carried by a prophage inserted at sbcB. However, alternative q(933)- or q(21)-related alleles were identified in the Australian stx(2c) prophage. Argentinean LI/II isolates were also distinguished from Australian isolates by the presence of the putative virulence determinant ECSP_3286 and the predominance of motile O157:H7 strains. Characteristics common to both Argentinean and Australian LI/II O157 strains included the presence of putative virulence determinants (ECSP_3620, ECSP_0242, ECSP_2687, ECSP_2870, and ECSP_2872) and the predominance of the tir255T allele. These data support further understanding of O157 phylogeny and may foster greater insight into the differential virulence of O157 lineages.
authors.affiliation: CSIRO Food and Nutritional Sciences, Archerfield BC, QLD, Australia.
authors.forename: Glen E
authors.initials: GE
authors.lastname: Mellor
authors.forename: Eby M
authors.initials: EM
authors.lastname: Sim
authors.forename: Robert S
authors.initials: RS
authors.lastname: Barlow
authors.forename: Beatriz A
authors.initials: BA
authors.lastname: D'Astek
authors.forename: Lucia
authors.initials: L
authors.lastname: Galli
authors.forename: Isabel
authors.initials: I
authors.lastname: Chinen
authors.forename: Marta
authors.initials: M
authors.lastname: Rivas
authors.forename: Kari S
authors.initials: KS
authors.lastname: Gobius
mesh_terms: D001118:Argentina; D001315:Australia; D003090:Coliphages / Q000235:genetics*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004927:Escherichia coli Infections / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity* / Q000821:virology*; D008969:Molecular Sequence Data; D039002:Prophages / Q000235:genetics*; D017422:Sequence Analysis, DNA; D022622:Shiga Toxin 1 / Q000235:genetics*; D022641:Shiga Toxin 2 / Q000235:genetics*; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2; D037521:Virulence Factors