title: Differential expression of stx2 variants in Shiga toxin-producing Escherichia coli belonging to seropathotypes A and C.
abstract: Only a subset of Shiga toxin (Stx)-producing Escherichia coli (STEC) are human pathogens, but the characteristics that account for differences in pathogenicity are not well understood. In this study, we investigated the distribution of the stx variants coding for Stx2 and its variants in highly virulent STEC of seropathotype A and low-pathogenic STEC of seropathotype C. We analysed and compared transcription of the corresponding genes, production of Shiga toxins, and stx-phage release in basal as well as in induced conditions. We found that the stx(2) variant was mainly associated with strains of seropathotype A, whereas most of the strains of seropathotype C possessed the stx(2-vhb) variant, which was frequently associated with stx(2), stx(2-vha) or stx(2c). Levels of stx(2) and stx(2)-related mRNA were higher in strains belonging to seropathotype A and in those strains of seropathotype C that express the stx(2) variant than in the remaining strains of seropathotype C. The stx(2-vhb) genes were the least expressed, in basal as well as in induced conditions, and in many cases did not seem to be carried by an inducible prophage. A clear correlation was observed between stx mRNA levels and stx-phage DNA in the culture supernatants, suggesting that most stx(2)-related genes are expressed only when they are carried by a phage. In conclusion, some relationship between stx(2)-related gene expression in vitro and the seropathotype of the STEC strains was observed. A higher expression of the stx(2) gene and a higher release of its product, in basal as well as in induced conditions, was observed in pathogenic strains of seropathotype A. A subset of strains of seropathotype C shows the same characteristics and could be a high risk to human health.
authors.affiliation: INRA, UR454 Unité de Microbiologie, 63122 St-Genès-Champanelle, France.
authors.forename: Thibaut
authors.initials: T
authors.lastname: de Sablet
authors.affiliation: INRA, UR454 Unité de Microbiologie, 63122 St-Genès-Champanelle, France.
authors.forename: Yolande
authors.initials: Y
authors.lastname: Bertin
authors.affiliation: INRA, UR454 Unité de Microbiologie, 63122 St-Genès-Champanelle, France.
authors.forename: Marjolaine
authors.initials: M
authors.lastname: Vareille
authors.affiliation: INRA, UR454 Unité de Microbiologie, 63122 St-Genès-Champanelle, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Girardeau
authors.affiliation: INRA, UR454 Unité de Microbiologie, 63122 St-Genès-Champanelle, France.
authors.forename: Annie
authors.initials: A
authors.lastname: Garrivier
authors.affiliation: INRA, UR454 Unité de Microbiologie, 63122 St-Genès-Champanelle, France.
authors.forename: Alain P
authors.initials: AP
authors.lastname: Gobert
authors.affiliation: INRA, UR454 Unité de Microbiologie, 63122 St-Genès-Champanelle, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Martin
mesh_terms: D003090:Coliphages / Q000235:genetics; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000235:genetics*; D014644:Genetic Variation; D012150:Polymorphism, Restriction Fragment Length; D012329:RNA, Bacterial / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012703:Serotyping; D022641:Shiga Toxin 2 / Q000096:biosynthesis* / Q000235:genetics*; D054323:Shiga-Toxigenic Escherichia coli / Q000145:classification* / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D022641:Shiga Toxin 2