title: Production of the subtilase AB5 cytotoxin by Shiga toxin-negative Escherichia coli.
abstract: The subtilase cytotoxin (SubAB) is an AB(5) toxin described in certain Shiga toxin (Stx)-producing Escherichia coli (STEC) strains that usually lack the locus for enterocyte effacement (LEE). We report for the first time the production of SubAB by two Stx-negative E. coli strains, isolated from unrelated cases of childhood diarrhea. The characterization of the SubAB-coding genes showed a 90% nucleotide sequence similarity with that of the prototype subAB, located on the virulence plasmid of the STEC O113 strain 98NK2 (pO113). In both strains, subAB was physically associated with tia, an invasion genetic determinant of enterotoxigenic E. coli. The strains were negative for the saa gene, encoding an adhesin located on pO113 and present in many of the SubAB-positive strains described so far. PCR screening of 61 STEC and 100 Stx-negative E. coli strains in our collection revealed the presence of subAB in five LEE-negative STEC strains but not in the Stx-negative strains. subAB was contiguous to tia in three of the positive strains, which were all negative for saa. These results indicate that SubAB production is not restricted to STEC and suggest that a subAB-tia putative pathogenicity island is involved in the dissemination of subAB genes, as an alternative to plasmid pO113.
authors: Dipartimento di Sanità Pubblica Veterinaria e Sicurezza Alimentare, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
authors: Rosangela
authors: R
authors: Tozzoli
authors: Alfredo
authors: A
authors: Caprioli
authors: Stefano
authors: S
authors: Cappannella
authors: Valeria
authors: V
authors: Michelacci
authors: Maria Luisa
authors: ML
authors: Marziano
authors: Stefano
authors: S
authors: Morabito
mesh_terms: D000595:Amino Acid Sequence; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D003967:Diarrhea / Q000382:microbiology*; D004926:Escherichia coli / Q000235:genetics* / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D010957:Plasmids; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013381:Subtilisins / Q000096:biosynthesis* / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D037521:Virulence Factors; D013381:Subtilisins; C527234:subtilase cytotoxin, E coli