Abstract
Adherent-invasive Escherichia coli (AIEC) strains carry virulence genes (VGs) which are rarely found in strains other than E. coli. These strains are abundantly found in gut mucosa of patients with inflammatory bowel disease (IBD); however, it is not clear whether their prevalence in the gut is affected by the diet of the individual. Therefore, in this study, we compared the population structure of E. coli and the prevalence of AIEC as well as the composition of gut microbiota in fecal samples of healthy participants (n = 61) on either a vegan (n = 34) or omnivore (n = 27) diet to determine whether diet is associated with the presence of AIEC. From each participant, 28 colonies of E. coli were typed using Random Amplified Polymorphic DNA (RAPD)–PCR. A representative of each common type within an individual was tested for the presence of six AIEC-associated VGs. Whole genomic DNA of the gut microbiota was also analyzed for its diversity profiles, utilizing the V5-V6 region of the16S rRNA gene sequence. There were no significant differences in the abundance and diversity of E. coli between the two diet groups. The occurrence of AIEC-associated VGs was also similar among the two groups. However, the diversity of fecal microbiota in vegans was generally higher than omnivores, with Prevotella and Bacteroides dominant in both groups. Whilst 88 microbial taxa were present in both diet groups, 28 taxa were unique to vegans, compared to seven unique taxa in the omnivores. Our results indicate that a vegan diet may not affect the number and diversity of E. coli populations and AIEC prevalence compared to omnivores. The dominance of Prevotella and Bacteroides among omnivores might be accounted for the effect of diet in these groups.
Highlights
Inflammatory bowel disease (IBD) represents a group of spontaneous, chronic inflammatory conditions of the gastrointestinal (GI) tract, including Crohn’s disease (CD), ulcerative colitis (UC), and, prospectively, colorectal cancer (CRC) [1]
59 clonal type (CT) and 30 single type (ST) were found among vegans, while 40 CTs and 18 STs were found among omnivores
The results indicated that all isolates within each CT carried identical virulence genes (VGs) profiles (Supplementary Table S3)
Summary
Inflammatory bowel disease (IBD) represents a group of spontaneous, chronic inflammatory conditions of the gastrointestinal (GI) tract, including Crohn’s disease (CD), ulcerative colitis (UC), and, prospectively, colorectal cancer (CRC) [1]. Recent studies indicate that mucosa-associated Escherichia coli are found in higher abundance in people with CD, CRC, and, to a lesser extent, UC [4] These strains, termed adherent-invasive E coli (AIEC), typically diffusely adhere (DA) to and invade intestinal epithelial cells in culture as well as survive and replicate within macrophages [5]. AIECs have been associated with specific virulence genes (VGs) that are not found, or rarely found, in other strains of E. coli [4] These include outer membrane protein C (ompC) and afimbrial adhesin C (afaC) that mediate diffuse adhesion to and invasion of GI epithelial cells and induce vascular endothelial growth factor expression, which contributes to angiogenesis and tumor development [4,6]. The presence of these bacteria in the GI tracts of healthy individuals may suggest a risk for development of IBD in susceptible hosts [9]
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