A Novel pAA Virulence Plasmid Encoding Toxins and Two Distinct Variants of the Fimbriae of Enteroaggregative Escherichia coli.

Rie Jønsson,Håvard Jenssen,Karen A Krogfelt,Erik J Boll,Nadia Boisen,Camilla A Sørensen,Katrine G Joensen,Carsten Struve,Flemming Scheutz,Betina H Jensen

doi:10.3389/fmicb.2017.00263

Rie Jønsson, Håvard Jenssen + Show 8 more

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https://doi.org/10.3389/fmicb.2017.00263

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Enteroaggregative Escherichia coli (EAEC) is an increasingly recognized pathogen associated with acute and persistent diarrhea worldwide. While EAEC strains are considered highly heterogeneous, aggregative adherence fimbriae (AAFs) are thought to play a pivotal role in pathogenicity by facilitating adherence to the intestinal mucosa. In this study, we optimized an existing multiplex PCR to target all known AAF variants, which are distinguished by differences in their pilin subunits. We applied the assay on a collection of 162 clinical Danish EAEC strains and interestingly found six, by SNP analysis phylogenetically distinct, strains harboring the major pilin subunits from both AAF/III and AAF/V. Whole-genome and plasmid sequencing revealed that in these six strains the agg3A and agg5A genes were located on a novel pAA plasmid variant. Moreover, the plasmid also encoded several other virulence genes including some not previously found on pAA plasmids. Thus, this plasmid endows the host strains with a remarkably high number of EAEC associated virulence genes hereby likely promoting strain pathogenicity.

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Enteroaggregative Escherichia coli (EAEC) is a common diarrheal organism and has been associated with acute and persistent diarrhea in a variety of settings (Cravioto et al, 1991; Cobeljic et al, 1996; Huppertz et al, 1997; Harrington et al, 2006; Scavia et al, 2008; Hebbelstrup Jensen et al, 2014)
EAEC strains were identified from the genes aatA, aggR, aaiC and aap targeted by multiplex PCR as previously described (Boisen et al, 2012)
The previously described multiplex detected several of the usher genes from AAF/I-IV, we decided only to include the genes encoding the five major pilin subunits and the usher found in AAF/III, AAF/IV or AAF/V which can be detected by a single primer set

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Enteroaggregative Escherichia coli (EAEC) is a common diarrheal organism and has been associated with acute and persistent diarrhea in a variety of settings (Cravioto et al, 1991; Cobeljic et al, 1996; Huppertz et al, 1997; Harrington et al, 2006; Scavia et al, 2008; Hebbelstrup Jensen et al, 2014). Enteroaggregative E. coli was first defined by its distinctive “stacked-brick” pattern of aggregative adherence (AA) to HEp-2 cells, mediated by the aggregative adherence fimbriae (AAFs; Nataro et al, 1992). The AAFs have been shown to promote biofilm formation and adhesion to various surfaces and are associated with inflammatory responses in the host (Sheikh et al, 2001; Harrington et al, 2005; Boisen et al, 2008; Farfan et al, 2008; Boll et al, 2012, 2013). The AAFs belong to the chaperone-usher family of adhesins, and consist of the pore-forming usher (encoded by agg3C in AAF/III), the chaperone (encoded by agg3D in AAF/III), the long fimbriae which consist of polymerized major pilin subunits (encoded by agg3A in AAF/III) and a minor pilin subunit at the tip (encoded by agg3B in AAF/III; Savarino et al, 1994; Berry et al, 2014)

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