title: Diversity of stx2 converting bacteriophages induced from Shiga-toxin-producing Escherichia coli strains isolated from cattle.
abstract: The presence of bacteriophages encoding Shiga toxin 2 (stx(2) phages) was analysed in 168 strains of Shiga-toxin-producing Escherichia coli (STEC) isolated from cattle. Following mitomycin C induction, strains carrying stx(2) phages were screened by plaque blot and hybridization with an stx(2)A-probe. In the stx(2)-phage-carrying strains, the amounts of phage production, phage DNA extracted and Stx(2) produced after induction were assessed. The induced stx(2) phages were characterized morphologically and genetically. Assays to obtain lysogens from different strains were also carried out and phages induced from the lysogens were compared with those induced from the STEC isolates. Results indicated that 18 % of the strains carried an inducible stx(2) phage. Most of them showed a direct relationship between phage induction and toxin production. Each strain carried only one inducible stx(2) phage, although a few strains had two copies of the stx(2) in the chromosome. The stx(2) phages showed diverse morphology and a wide variability in their genome. Assays to obtain lysogens showed that not all the phages were transduced with the same frequency and only six lysogens were obtained. Phages in the lysogens were the same as those induced from their respective initial STEC host strains, although the induction and relative toxin production of the lysogens varied. Most phages carried the stx(2) gene, while a few carried stx(2) variants. Infectivity of the phages depended on the different hosts, although O157 : H7 was preferentially infected by phages induced from O157 strains. The results show that inducible stx(2) phages are common among STEC of animal origin and that they may enhance the spread of stx(2).
authors.affiliation: Department of Microbiology, University of Barcelona, Diagonal 645, E-08028 Barcelona, Spain.
authors.forename: Maite
authors.initials: M
authors.lastname: Muniesa
authors.affiliation: Laboratorio de Referencia de E. coli (LREC), Departamento de Microbiología y Parasitología, Facultad de Veterinaria, Universidad de Santiago de Compostela, 27002 Lugo, Spain.
authors.forename: Jesus E
authors.initials: JE
authors.lastname: Blanco
authors.affiliation: Servei Microbiologia, Laboratori de l'Agència de Salut Pública de Barcelona, Drassanes 13, E-08001 Barcelona, Spain.
authors.forename: Merce
authors.initials: M
authors.lastname: de Simón
authors.affiliation: Department of Microbiology, University of Barcelona, Diagonal 645, E-08028 Barcelona, Spain.
authors.forename: Ruth
authors.initials: R
authors.lastname: Serra-Moreno
authors.affiliation: Department of Microbiology, University of Barcelona, Diagonal 645, E-08028 Barcelona, Spain.
authors.forename: Anicet R
authors.initials: AR
authors.lastname: Blanch
authors.affiliation: Department of Microbiology, University of Barcelona, Diagonal 645, E-08028 Barcelona, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Jofre
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000942:Antigens, Bacterial / Q000032:analysis; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology; D003090:Coliphages / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology / Q000648:ultrastructure; D004279:DNA, Viral / Q000032:analysis / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification / Q000821:virology*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000302:isolation & purification / Q000821:virology; D005814:Genes, Viral; D014644:Genetic Variation; D008242:Lysogeny; D016685:Mitomycin / Q000494:pharmacology; D008969:Molecular Sequence Data; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D019081:O Antigens / Q000032:analysis; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D022641:Shiga Toxin 2 / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*
chemical_list: D000942:Antigens, Bacterial; D004279:DNA, Viral; C022863:H antigen; D019384:Nucleic Acid Synthesis Inhibitors; D019081:O Antigens; D022641:Shiga Toxin 2; D016685:Mitomycin