title: Identification of two allelic variants of toxB gene and investigation of their distribution among Verocytotoxin-producing Escherichia coli.
abstract: Verocytotoxin-producing Escherichia coli (VTEC) are food borne pathogens causing severe human infections. The virulence genes asset of VTEC is complex and has not been completely defined yet. Nonetheless, all the virulence genes described so far have been described as conveyed by mobile genetic elements. A gene, termed toxB, has been identified in a large virulence plasmid of VTEC O157, later described in similar plasmids carried by VTEC O26 and O145. In this study we identified for the first time an intact copy of toxB gene in a plasmid present in a VTEC O111 strain and observed the existence of two allelic variants of the gene, that we termed toxB1 and toxB2. We investigated the distribution of the two alleles in a panel of VTEC strains belonging to different serogroups and demonstrated that this gene is present only in VTEC serogroups associated with the most severe forms of the infections such as those belonging to the five serogroups O157, O26, O111, O103 and O145 and that the two alleles segregate with the serogroup of the hosting strains. In particular the toxB1 variant was only present in VTEC O157 while the toxB2 allele was present in the remaining four VTEC serogroups.
authors.affiliation: Istituto Superiore di Sanità, Dipartimento di Sanità Pubblica Veterinaria e Sicurezza Alimentare, Rome, Italy. Electronic address: valeria.michelacci@iss.it.
authors.forename: Valeria
authors.initials: V
authors.lastname: Michelacci
authors.affiliation: Istituto Superiore di Sanità, Dipartimento di Sanità Pubblica Veterinaria e Sicurezza Alimentare, Rome, Italy; Department of Biology, University 'Roma Tre', Roma, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Grande
authors.affiliation: Istituto Superiore di Sanità, Dipartimento di Sanità Pubblica Veterinaria e Sicurezza Alimentare, Rome, Italy.
authors.forename: Rosangela
authors.initials: R
authors.lastname: Tozzoli
authors.affiliation: Istituto Superiore di Sanità, Dipartimento di Sanità Pubblica Veterinaria e Sicurezza Alimentare, Rome, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Maugliani
authors.affiliation: Istituto Superiore di Sanità, Dipartimento di Sanità Pubblica Veterinaria e Sicurezza Alimentare, Rome, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Caprioli
authors.affiliation: Istituto Superiore di Sanità, Dipartimento di Sanità Pubblica Veterinaria e Sicurezza Alimentare, Rome, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Morabito
mesh_terms: D000483:Alleles; D000818:Animals; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary; D029968:Escherichia coli Proteins / Q000235:genetics*; D005517:Foodborne Diseases / Q000382:microbiology; D005838:Genotype; D006801:Humans; D010957:Plasmids; D065288:Serogroup; D054323:Shiga-Toxigenic Escherichia coli / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D037521:Virulence Factors / Q000235:genetics*
chemical_list: D029968:Escherichia coli Proteins; D037521:Virulence Factors; C439629:toxB protein, E coli
keywords: Plasmid; Seropathotype; VTEC; Virulence; toxB