Abstract
Enteroaggregative E. coli (EAEC) is an established diarrhoeagenic pathotype. The association with virulence gene content and ability to cause disease has been studied but little is known about the population structure of EAEC and how this pathotype evolved. Analysis by Multi Locus Sequence Typing of 564 EAEC isolates from cases and controls in Bangladesh, Nigeria and the UK spanning the past 29 years, revealed multiple successful lineages of EAEC. The population structure of EAEC indicates some clusters are statistically associated with disease or carriage, further highlighting the heterogeneous nature of this group of organisms. Different clusters have evolved independently as a result of both mutational and recombination events; the EAEC phenotype is distributed throughout the population of E. coli.
Highlights
The definition of Enteroaggregative E. coli (EAEC) varies in studies which either use its aggregative adherence (AA) phenotype on HEp-2 cells [1], the CVD432 probe [2] or PCR to detect the anti-aggregative transporter gene [3] or the EAEC regulatory gene [4] or a combination of phenotype and genotype
‘Strains from this study not previously described include archived clinical strains received by Gastrointestinal Bacteria Reference Unit (GBRU) for typing between 1985–1995, Outbreak E of enteroaggregative E. coli that occurred in Bangladesh in 1998, recent clinical strains received by GBRU for typing between 2009–2013. #EAEC were defined as having the aat and/or aggR gene
Evolution of Enteroaggregative E. coli predominantly associated with sequence types (STs) (O7:H4-ST484, O104:H4-ST678, O111:H21ST40, O125ac:H9-ST295, O153:H30-ST38,) while others were found in multiple STs (O44:H18-ST449, ST414, ST30, O126:H27-ST200 & single locus variants (SLV), ST155, O166:H15ST349 & SLV/double locus variants (DLV), ST130, ST394,)
Summary
The definition of EAEC varies in studies which either use its aggregative adherence (AA) phenotype on HEp-2 cells [1], the CVD432 probe [2] or PCR to detect the anti-aggregative transporter (aat) gene [3] or the EAEC regulatory gene (aggR) [4] or a combination of phenotype and genotype. Evolution of Enteroaggregative E. coli have been associated with diarrhoea in epidemiological studies and outbreaks. A comprehensive study looking at the relationship between phylogeny from case or healthy carriage in multiple countries has not been performed and there has been limited analysis of EAEC at the population level. The most detailed study on EAEC population analysis was in Nigeria and was carried out to find an association with EAEC complexes and disease in children under 5 with links to virulence genes, resistance and plasmid groups [7]. Results indicated that the range of sequence types (STs) associated with EAEC is very large and disease, only within a specific age-group, was linked to ST10, an ST associated with multiple E. coli pathotypes. There were no reported associations between disease and, virulence genes, resistance profiles, nor plasmid compatibility groups
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