Development of a one-step PCR assay with nine primer pairs for the detection of five diarrheagenic Escherichia coli types.

Diarrheal diseases are extraordinarily common with a worldwide distribution, and diarrheagenic Escherichia coli (E. coli) strains are important causative agents [3]. Five types of diarrheagenic E. coli have been identified, namely enterohemorrhagic E. coli (EHEC), enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enteroaggregative E. coli (EAEC), and enteroinvasive E. coli (EIEC) [11]. The major virulence factor, which is also a defining characteristic of EHEC, is Shiga toxin (Stx). Shiga toxin-producing E. coli (STEC) strains produce one or both of the two major types of Shiga toxins, designated Stx1 and Stx2. Production of Stx2 is associated with an increased risk of developing the hemolytic-uremic syndrome [20]. Sequence homologies for the A and B subunits are 55% and 57% for the prototypical Stx1 and Stx2 toxins, respectively [11, 13]. ETEC strains are identified by the ability to produce enterotoxins; the heatlabile toxin (LT) and the heat-stable toxin (ST) [19]. The LT toxin is encoded by eltAB, and the ST toxin is encoded by two different genes, estA and st1, which produce STh (originally isolated from ETEC in humans) and STp (originally from a pig isolate) [8, 10, 11]. EPECs can be classified as typical or atypical based on the production of bundle-forming pili (BFP) encoded by the Escherichia adherence factor (EAF) gene [11]. Atypical EPEC strains would possess the eae gene that correlates with possession of the 35 kb locus of enterocyte effacement (LEE) pathogenicity island responsible for the attaching and effacing (A/E) effect [22]. A 1 kb fragment of the 60–65 MDa virulence Received: December 12, 2013 Revised: February 28, 2014 Accepted: March 13, 2014