DNA sequence and analysis of a 90.1-kb plasmid in Shiga toxin-producing Escherichia coli (STEC) O145:NM 83-75

Shiga toxin-producing Escherichia coli (STEC) strains belonging to serogroup O145 are important emerging food-borne pathogens responsible for sporadic cases and outbreaks of hemorrhagic colitis and hemolytic uremic syndrome. A large plasmid carried by STEC O145:NM strain 83-75 and named pO145-NM was sequenced, and the genes were annotated. pO145-NM is 90,103 bp in size and carries 89 open reading frames. Four genes/regions in pO145-NM encode for STEC virulence factors, including toxB (protein involved in adherence), espP (a serine protease), katP (catalase peroxidase), and the hly (hemolysin) gene cluster. These genes have also been identified in large virulence plasmids found in other STEC serogroups, including O26, O157, O111, and O103. pO145-NM carries the espPα subtype that is associated with STEC strains that cause more severe disease. Phylogenetic analyses of HlyB, EspP, and ToxB in various STEC strains showed a high degree of similarity of these proteins in E. coli serotypes O145:NM, O26:H11/H−, O111:NM/H−, and O157:H7 potentially placing these STEC into a related group.

► Sequence and genes of the virulence plasmid in STEC Escherichia coli O145:NM were determined.
► pO145-NM (90,103 bp) carried the hlyCABD operon and toxB, katP, espP virulence genes.
► Phylogenetic analysis of virulence genes place O145, O157, O111, and O26 in a related group.
► Findings elucidate genetic fingerprints that assist in identifying pathogenic STEC.