title: Bacteriophage-encoding cytolethal distending toxin type V gene induced from nonclinical Escherichia coli isolates.
abstract: Cytolethal distending toxin (Cdt) is produced by a variety of pathogenic bacteria, including pathogenic serotypes of Shiga toxin-producing Escherichia coli (STEC). The Cdt family comprises five variants (Cdt-I to Cdt-V) encoded by three genes located within the chromosome or plasmids or, in the case of Cdt-I, within bacteriophages. In this study, we evaluated the occurrence of the cdt gene in a collection of 140 environmental STEC isolates. cdt was detected in 12.1% of strains, of which five strains carried inducible bacteriophages containing the Cdt-V variant. Two Cdt-V phages of the Siphoviridae morphology lysogenized Shigella sonnei, generating two lysogens: a single Cdt phage lysogen and a double lysogen, containing a Cdt phage and an Stx phage, both from the wild-type strain. The rates of induction of Cdt phages were evaluated by quantitative PCR, and spontaneous induction of Cdt-V phage was observed, whereas induction of Stx phage in the double lysogen was mitomycin C dependent. The Cdt distending effect was observed in HeLa cells inoculated with the supernatant of the Cdt-V phage lysogen. A ClaI fragment containing the cdt-V gene of one phage was cloned, and sequencing confirmed the presence of Cdt-V, as well as a fragment downstream from the cdt homolog to gpA, encoding a replication protein of bacteriophage P2. Evaluation of Cdt-V phages in nonclinical water samples showed densities of 10(2) to 10(9) gene copies in 100 ml, suggesting the high prevalence of Cdt phages in nonclinical environments.
authors.affiliation: Department of Microbiology, University of Barcelona, Diagonal 645, Annex, Floor 0, 08028 Barcelona, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Allué-Guardia
authors.forename: Cristina
authors.initials: C
authors.lastname: García-Aljaro
authors.forename: Maite
authors.initials: M
authors.lastname: Muniesa
mesh_terms: D001427:Bacterial Toxins / Q000096:biosynthesis* / Q000235:genetics / Q000633:toxicity; D003090:Coliphages / Q000235:genetics* / Q000302:isolation & purification* / Q000648:ultrastructure; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008242:Lysogeny; D016685:Mitomycin / Q000378:metabolism; D008969:Molecular Sequence Data; D039002:Prophages / Q000187:drug effects; D017422:Sequence Analysis, DNA; D054323:Shiga-Toxigenic Escherichia coli / Q000821:virology*; D012764:Shigella sonnei / Q000821:virology; D017906:Siphoviridae / Q000235:genetics / Q000302:isolation & purification / Q000648:ultrastructure; D014764:Viral Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000633:toxicity; D014775:Virus Activation
chemical_list: D001427:Bacterial Toxins; D004279:DNA, Viral; D014764:Viral Proteins; C067044:cytolethal distending toxin; D016685:Mitomycin