Abstract
Escherichia coli strains belonging to serogroups O1 and O2 are frequently associated with human infections, especially extra-intestinal infections such as bloodstream infections or urinary tract infections. These strains can be associated with a large array of flagellar antigens. Because of their frequency and clinical importance, a reliable detection of E. coli O1 and O2 strains and also the frequently associated K1 capsule is important for diagnosis and source attribution of E. coli infections in humans and animals. By sequencing the O-antigen clusters of various O1 and O2 strains we showed that the serogroups O1 and O2 are encoded by different sets of O-antigen encoding genes and identified potentially new O-groups. We developed qPCR-assays to detect the various O1 and O2 variants and the K1-encoding gene. These qPCR assays proved to be 100% sensitive and 100% specific and could be valuable tools for the investigations of zoonotic and food-borne infection of humans with O1 and O2 extra-intestinal (ExPEC) or Shiga toxin-producing E. coli (STEC) strains.
Highlights
Strains of the E. coli species are currently divided into 183 O-groups and 53 H-types (Joensen et al, 2015)
We investigated extraintestinal pathogenic E. coli (ExPEC), enteropathogenic E. coli (EPEC), and Shiga toxin-producing E. coli (STEC) strains of serogroup O1 and O2 for their O-antigen encoding genes to explore the nature of different antigens described for O1 and to explain the cross-reactivity between O1, O2, and other E. coli O-groups
A qPCR was developed for the E. coli wzyO1 gene derived from the sequence of the E. coli O1 strain G1632 (U5-41) (Li et al, 2010; GenBank Accession GU299791; Table 1)
Summary
Strains of the E. coli species are currently divided into 183 O-groups (lipopolysaccharide) and 53 H-types (flagellar antigen) (Joensen et al, 2015). The size and gene content of the O-AGC vary between serogroups, and two genes, wzx (O-antigen flippase) and wzy (O-antigen polymerase) or wzm (O-antigen ABC transporter permease gene) and wzt (ABC transporter ATP-binding gene), appear highly specific for each serogroup. These can serve as targets for molecular determination of the serogroup by PCR, qPCR or nucleotide sequencing (Iguchi et al, 2015b; Joensen et al, 2015; Fratamico et al, 2016). Molecular serotyping, targeting genes involved in surface antigen synthesis, appears to be a rapid, specific and cheaper alternative to conventional serotyping
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