Campylobacter concisus and exotoxin 9 levels in paediatric patients with Crohn’s disease and their association with the intestinal microbiota

There is mounting evidence for a possible role for Campylobacter concisus in Crohn’s disease (CD). However, the pathogenic potential of C. concisus remains disputed due to its presence in healthy subjects. It is documented that genetic diversity exists within this species, with some strains possessing putative virulence determinants such as exotoxin 9/DnaI that may enable them to persist intracellularly in host cells. In order to clarify this, we employed real-time PCR to determine C. concisus and exotoxin 9 levels within faecal samples of CD patients and healthy controls, and correlated these levels with abundances of microbial taxa identified in a subset of subjects. Both C. concisus and exotoxin 9 levels were found to be higher in CD patients than healthy controls, suggesting not only that CD patients had a greater abundance of C. concisus but also that their strains were likely to be more virulent. Moreover, C. concisus levels correlated with the exotoxin 9 levels in CD patients but not in healthy controls, indicating that healthy controls were colonized by non-virulent C. concisus strains. Correlations with the intestinal microbiota found C. concisus levels to correlate with Eubacterium, Subdoligranulum and Blautia, while exotoxin 9 levels correlated with Dialister, Oscillospira, Lachnospira and Prevotella. This suggests that either the composition of the intestinal microbial flora has the ability to influence levels of both virulent and non-virulent C. concisus strains, or infection with C. concisus may modulate the levels of specific bacterial taxa within the gastrointestinal tract.