Pathogenic Potential of Campylobacter ureolyticus

Abstract

ABSTRACTThe recent detection and isolation of the aflagellateCampylobacter ureolyticus(previously known asBacteroides ureolyticus) from intestinal biopsy specimens and fecal samples of children with newly diagnosed Crohn's disease led us to investigate the pathogenic potential of this bacterium. Adherence and gentamicin protection assays were employed to quantify the levels of adherence to and invasion into host cells.C. ureolyticusUNSWCD was able to adhere to the Caco-2 intestinal epithelial cell line with a value of 5.341% ± 0.74% but was not able to invade the Caco-2 cells. The addition of two proinflammatory cytokines, tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ), to the cell line did not affect attachment or invasion, with attachment levels being 4.156% ± 0.61% (P= 0.270) for TNF-α and 6.472% ± 0.61% (P= 0.235) for IFN-γ. Scanning electron microscopy visually confirmed attachment and revealed thatC. ureolyticusUNSWCD colonizes and adheres to intestinal cells, inducing cellular damage and microvillus degradation. Purification and identification of theC. ureolyticusUNSWCD secretome detected a total of 111 proteins, from which 29 were bioinformatically predicted to be secretory proteins. Functional classification revealed three putative virulence and colonization factors: the surface antigen CjaA, an outer membrane fibronectin binding protein, and an S-layer RTX toxin. These results suggest thatC. ureolyticushas the potential to be a pathogen of the gastrointestinal tract.