Abstract
BackgroundCrohn's disease (CD) is a high morbidity chronic inflammatory disorder of unknown aetiology. Adherent-invasive Escherichia coli (AIEC) has been recently implicated in the origin and perpetuation of CD. Because bacterial biofilms in the gut mucosa are suspected to play a role in CD and biofilm formation is a feature of certain pathogenic E. coli strains, we compared the biofilm formation capacity of 27 AIEC and 38 non-AIEC strains isolated from the intestinal mucosa. Biofilm formation capacity was then contrasted with the AIEC phenotype, the serotype, the phylotype, and the presence of virulence genes.ResultsSpecific biofilm formation (SBF) indices were higher amongst AIEC than non-AIEC strains (P = 0.012). In addition, 65.4% of moderate to strong biofilms producers were AIEC, whereas 74.4% of weak biofilm producers were non-AIEC (P = 0.002). These data indicate that AIEC strains were more efficient biofilm producers than non-AIEC strains. Moreover, adhesion (P = 0.009) and invasion (P = 0.003) indices correlated positively with higher SBF indices. Additionally, motility (100%, P < 0.001), H1 type flagellin (53.8%, P < 0.001), serogroups O83 (19.2%, P = 0.008) and O22 (26.9%, P = 0.001), the presence of virulence genes such as sfa/focDE (38.5%, P = 0.003) and ibeA (26.9%, P = 0.017), and B2 phylotype (80.8%, P < 0.001) were frequent characteristics amongst biofilm producers.ConclusionThe principal contribution of the present work is the finding that biofilm formation capacity is a novel, complementary pathogenic feature of the recently described AIEC pathovar. Characterization of AIEC specific genetic determinants, and the regulatory pathways, involved in biofilm formation will likely bring new insights into AIEC pathogenesis.
Highlights
Crohn's disease (CD) is a high morbidity chronic inflammatory disorder of unknown aetiology
adherent-invasive E. coli (AIEC) strains are stronger biofilm producers than non-AIEC strains isolated from the intestinal mucosa The present study involved a collection of 65 E. coli strains, 27 of which (41.5%) were classified as AIEC by their ability to adhere to and invade intestinal epithelial cells, and to survive and replicate within macrophages, as previously described [11] (Table 1)
Within the category of weak biofilm producers, 74.4% of strains were non-AIEC, whereas 65.4% of moderate to strong biofilm producers were AIEC (P = 0.002)
Summary
Crohn's disease (CD) is a high morbidity chronic inflammatory disorder of unknown aetiology. Adherent-invasive Escherichia coli (AIEC) has been recently implicated in the origin and perpetuation of CD. The aetiology of CD remains elusive to date, it is widely accepted that several factors are involved in the onset or perpetuation of the disease. These factors include genetic and immunologic features that confer host susceptibility, and external or environmental factors such as microorganisms and lifestyle [2,3]. Adherent-invasive E. coli (AIEC) is increasing in relevance because it has been reported to be more prevalent in CD patients than in controls in several countries (France [11], United Kingdom [12], USA [13,14], and Spain [15]). AIEC pathovar has been speculated to be closely related to ExPEC pathovar
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