Submitted to: Plasmid Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/12/2012
Publication Date: 2/19/2012
Citation: Yan, X., Fratamico, P.M., Needleman, D.S., Bayles, D.O. 2012. DNA sequence and analysis of a 90.1 kb virulence plasmid in shiga toxin-producing Escherichia coli (STEC) O145:NM 83-75. Plasmid Journal. 68:25-32. Interpretive Summary: Escherichia coli strains that produce Shiga toxins and belong to a specific type or serogroup known as O145 are important human pathogens that cause hemorrhagic colitis and hemolytic uremic syndrome. These bacteria cause a similar type of food-borne illness as Shiga toxin-producing E. coli (STEC) O157:H7; however, it is not known if STEC O145 and E. coli O157:H7 possess the same set of genes (virulence genes) that are important for causing illness. STEC O157:H7 possesses a large plasmid (circular DNA that is not part of the chromosome) that carries important virulence genes; however it is not known if E. coli O145 strains that cause human illness also possess a large virulence plasmid. Therefore, the DNA sequence of the large virulence plasmid of STEC O145:NM strain 83-75 that was associated with human illness was determined and analyzed. The E. coli O145 strain had a similar set of virulence genes as the large plasmid of E. coli O157:H7, and it was demonstrated the serogroups O157, O26, and O145 formed a closely related group. This study underscores the potential importance of the virulence plasmid in the disease process of one of the most important STEC serogroups and provides essential information to develop diagnostic tools for the rapid identification of highly pathogenic strains.
Technical Abstract: Shiga toxin-producing Escherichia coli (STEC) 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 carried the espPa gene that is associated with STEC strains that cause more severe disease. Phylogenetic analyses of plasmid-encoded hlyB, katP, espP, and toxB place E. coli serotypes O145:NM, O26:H11, and O157:H7 into a closely related group.