title: Relative cytotoxicity of Escherichia coli O157:H7 isolates from beef cattle and humans.
abstract: Differences and similarities between Escherichia coli O157:H7 isolates from beef cattle and those from sporadic human outbreaks are not fully elucidated. Here, we compared 44 O157:H7 isolates of bovine and human origins (22 isolates of each) to better understand their cytotoxic potential. The Shiga toxin genes stx1, stx2, or both were detected in the 44 isolates, and all elicited Vero cell cytotoxicity. The greatest cytotoxicity was caused by bovine isolates having only stx2 and which represented the majority of such isolates (81.8%). However, no correlation was found between the level of stx gene transcription and cytotoxicity. All human and bovine isolates possessed variant type stx2 and stx2c, respectively, as determined by PCR-restriction fragment length polymorphism. Isolates harboring both stx1 and stx2 genes were much more frequent in human isolates (86.4%). The combination stx1-stx2c found in only four bovine isolates was less cytotoxic. It is clear that cytotoxicity alone cannot account for the apparent inability of O157:H7 bovine isolates to cause diseases in humans. We have found that stx1-stx2-containing or stx1-stx2c-containing isolates were less cytotoxic than several bovine isolates having only stx2c, suggesting that the stx gene combination or other virulence genes in specific genetic lineages may affect the disease outcome.
authors.affiliation: Département de Biologie, Centre d'Etudes et de Valorisation de la Diversité Microbienne, Université de Sherbrooke, Canada.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Lefebvre
authors.forename: Moussa S
authors.initials: MS
authors.lastname: Diarra
authors.forename: Caroline
authors.initials: C
authors.lastname: Vincent
authors.forename: Hélène
authors.initials: H
authors.lastname: Moisan
authors.forename: François
authors.initials: F
authors.lastname: Malouin
mesh_terms: D000818:Animals; D002417:Cattle / Q000382:microbiology*; D016923:Cell Death / Q000187:drug effects*; D002522:Chlorocebus aethiops; D003092:Colitis / Q000382:microbiology; D004269:DNA, Bacterial / Q000032:analysis; D004927:Escherichia coli Infections / Q000382:microbiology; D019453:Escherichia coli O157 / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity*; D005243:Feces / Q000382:microbiology; D015870:Gene Expression; D006801:Humans; D008460:Meat / Q000382:microbiology; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D022622:Shiga Toxin 1 / Q000235:genetics / Q000633:toxicity*; D022641:Shiga Toxin 2 / Q000235:genetics / Q000633:toxicity*; D014709:Vero Cells / Q000187:drug effects
chemical_list: D004269:DNA, Bacterial; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2