Similarity and Divergence among Adherent-Invasive Escherichia coli and Extraintestinal Pathogenic E. coli Strains

Abstract

Adherent-invasive Escherichia coli (AIEC) pathovar strains, which are associated with Crohn's disease, share many genetic and phenotypic features with extraintestinal pathogenic E. coli (ExPEC) strains, but little is known about the level of genetic similarity between the two pathovars. We aimed to determine the frequency of strains with the "AIEC phenotype" among a collection of ExPEC strains and to further search for a common phylogenetic origin for the intestinal and extraintestinal AIEC strains. The adhesion, invasion, and intramacrophage replication capabilities (AIEC phenotype) of 63 ExPEC strains were determined. Correlations between virulence genotype and AIEC phenotype and between intestinal/extraintestinal origin, serotype, and phylogroup were evaluated for the 63 ExPEC and 23 intestinal AIEC strains. Phylogenetic relationships between extraintestinal and intestinal AIEC strains were determined using multilocus sequence typing (MLST) and pulsed-field gel electrophoresis. Only four (6.35%) ExPEC strains, belonging to the O6:H1, O83:H1, and O25:H4 serotypes, were classified as having an AIEC phenotype. These strains were found to be genetically related to some intestinal AIEC strains of the same serotypes as revealed by MLST. No particular virulence gene sets correlated with the intestinal/extraintestinal origin of the strains or with the AIEC phenotype, whereas the gene sets did correlate with the serogroup. We identified two intestinal AIEC strains and one extraintestinal AIEC strain belonging to the O25:H4 serotype that also belonged to the emerging and virulent clonal group ST131. In conclusion, the ExPEC and AIEC pathovars share similar virulence gene sets, and certain strains are phylogenetically related. However, the majority of ExPEC strains did not behave like AIEC strains, thus confirming that the AIEC pathovar possesses virulence-specific features that, to date, are detectable only phenotypically.Members of the Enterobacteriaceae family, especially Escherichia coli, have been repeatedly suggested to play a role in the origin and/or perpetuation of Crohn's disease (CD). In part, this suggestion was based on the higher abundance of this bacterium in CD patients than in control subjects (4,10,20,23,28,29,32,41,48,51). Although considerable effort has been devoted to the search for intestinal pathogenic E. coli strains associated with CD, to date none of the six previously described pathovars (27) has been implicated in this condition. observed that E. coli strains with adhesion and invasion properties colonized the ileal mucosae of CD patients more frequently than those of control subjects. Darfeuille-Michaud et al. further characterized these strains and proposed a new potential E. coli pathovar associated with CD, which was designated adherent-invasive E. coli (AIEC) (10). The implication of AIEC in CD is becoming increasingly relevant because several independent studies from different countries have reported a higher prevalence of invasive E. coli in CD patients (4,17,33,34,47).The main chara...

Escherichia coli ST131, an Intriguing Clonal Group

“…Martinez-Medina et al, who characterized the similarity and divergence of adherent invasive E. coli (AIEC) and ExPEC strains, found that one of the 12 ExPEC ST131 strains tested had an AIEC phenotype and displayed 50% similarity to two other ST131 AEIC strains (128). The VF genes harbored by these three strains were different, suggesting that ST131 AIEC strains, like other AIEC strains, have virulencespecific features that can currently be detected only phenotypically.…”

Infection strategies of enteric pathogenic Escherichia coli

“…While AIEC strains are genetically related to ExPEC strains they appear to have acquired novel virulence-specific features which can be characterized phenotypically (adhesion, invasion and intramacrophage replication) but the genetic basis of which is still largely undetermined. 81 This has hampered identification and hence research into the prevalence and importance of AIEC. The majority of AIEC research has used a single strain, LF82, and extrapolation of these results to other AIEC strains is vital as the field progresses.…”

Studies on avian pathogenic Escherichia coli in commercial broiler chicken in South East Queensland

“…This is of public health significance as these genes that encode for critically important antimicrobial resistance can be transmitted to other bacterial species by horizontal gene transfer (HGT) (Allen et al, 2013;Boerlin and Reid-Smith, 2008;da Costa et al, 2013;Davies, 1994;Martinez-Medina et al, 2009). Further investigations are needed to identify the plasmids associated with the ARGs among E. coli isolates sourced from chickens in Australia.…”