Stx2 subtyping of Shiga toxin-producing Escherichia coli isolated from cattle in France: detection of a new Stx2 subtype and correlation with additional virulence factors.
At least 11 Stx2 variants produced by Shiga toxin-producing Escherichia coli (STEC) isolated from patients and animals have been described. The Stx2 subtyping of STEC isolated from healthy cows positive for stx(2) (n = 104) or stx(2) and stx(1) (n = 63) was investigated. Stx2vh-b, Stx2 (renamed Stx2-EDL933), and Stx2vh-a were the subtypes mostly detected among the bovine isolates (39.5, 39, and 25.5%, respectively). Stx2e was not present, and subtypes included in the Stx2d group (Stx2d-OX3a, Stx2d-O111, and Stx2d-Ount) were found infrequently among the isolates examined (8.5%). A combination of two distinct Stx2 subtypes was observed among 23.5% of the strains. For the first time, a combination of three subtypes (Stx2-EDL933/Stx2vh-b/Stx2d and Stx2vh-a/Stx2vh-b/Stx2d) was detected (3.5% of the isolates). In addition, bovine STEC harboring stx(1) and one or two stx(2) genes appeared highly cytotoxic toward Vero cells. A new Stx2 subtype (Stx2-NV206), present among 14.5% of the isolates, showed high cytotoxicity for Vero cells. Two amino acid residues (Ser-291 and Glu-297) important for the activation of Stx2 by human intestinal mucus were conserved on the Stx2-NV206 A subunit. The gene encoding Ehx enterohemolysin was prominent among STEC harboring stx(2)-EDL933 alone (78%) or a combination of stx(2)-EDL933 and stx(2)vh-b (85%). In addition, Stx2-EDL933 and/or Stx2vh-b subtypes were highly associated with other putative virulence factors such as Stx1 and EspP extracellular serine protease, but not with EAST1 enterotoxin.
Bertin
Y
Y
Laboratoire de Microbiologie, Centre de Recherche INRA de Clermont-Ferrand-Theix, 63122 St-Genès Champanelle, France. bertin@clermont.inra.fr
Boukhors
K
K
Pradel
N
N
Livrelli
V
V
Martin
C
C
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D002522:Chlorocebus aethiops; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D004926:Escherichia coli / Q000145:classification* / Q000378:metabolism / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D005602:France; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D017422:Sequence Analysis, DNA; D022641:Shiga Toxin 2 / Q000145:classification* / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D014709:Vero Cells; D014774:Virulence
D004269:DNA, Bacterial; D022641:Shiga Toxin 2