title: The cytolethal distending toxin-IV cdt coding region in an avian pathogenic Escherichia coli (APEC) strain shows instability and irregular excision pattern.
abstract: Cytolethal distending toxins (CDT) represent an emerging toxin family, widely distributed among pathogenic bacteria. The cdtABC genes in E. coli are either part of the genome of prophages, plasmid or pathogenicity island. In order to investigate the stability and the transfer potential of cdt-IV genes cdtB gene was replaced by chloramphenicol (Cm) resistance encoding cat gene in the avian pathogenic E. coli (APEC) strain E250. After consecutive passages in non-selective medium at 37 °C 7.6% (219/2900) of the investigated colonies of E250::cat strain became Cm-sensitive (Cm(S)). To reveal deletion mechanism 177 Cm(S) colonies were investigated for presence of cdtA, cdtC and cdtC associated gene by PCR. One hundred and sixteen colonies of the Cm(S) colonies (65.5%) showed partial or complete deletion in the cdt-IV region. Progressive loss of the upstream genes of the cdt cluster in E250 compared to other CDT-IV producing APEC strains and the fact that all the potential deletion patterns were identified, suggests the presence of an unstable hitherto unknown genomic region. The failure of in vitro transfer of cdt genes into a porcine EPEC E. coli strain suggests that the deletion of cdt-IV flanking genes alone do not promote the spread of cdt-IV.
authors.affiliation: Institute for Veterinary Medical Research, Agricultural Research Centre, Hungarian Academy of Sciences , Budapest , Hungary.
authors.forename: István
authors.initials: I
authors.lastname: Tóth
authors.affiliation: Institute of Medical Microbiology and Immunology, University of Pécs , Pécs , Hungary.
authors.forename: György
authors.initials: G
authors.lastname: Schneider
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics* / Q000378:metabolism; D001715:Bird Diseases / Q000382:microbiology; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D017353:Gene Deletion; D016366:Open Reading Frames; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology
chemical_list: D001427:Bacterial Toxins; D029968:Escherichia coli Proteins; C067044:cytolethal distending toxin
keywords: Escherichia coli; cytolethal distending toxin (CDT); locus instability