Campylobacter concisus - A new player in intestinal disease

Abstract

Over the last decade Campylobacter concisus, a highly fastidious member of the Campylobacter genus has been described as an emergent pathogen of the human intestinal tract. Historically, C. concisus was associated with the human oral cavity and has been linked with periodontal lesions, including gingivitis and periodontitis, although currently its role as an oral pathogen remains contentious. Evidence to support the role of C. concisus in acute intestinal disease has come from studies that have detected or isolated C. concisus as sole pathogen in fecal samples from diarrheic patients. C. concisus has also been associated with chronic intestinal disease, its prevalence being significantly higher in children with newly diagnosed Crohn's disease (CD) and adults with ulcerative colitis than in controls. Further C. concisus has been isolated from biopsy specimens of patients with CD. While such studies support the role of C. concisus as an intestinal pathogen, its isolation from healthy individuals, and failure of some studies to show a significant difference in C. concisus prevalence in subjects with diarrhea and healthy controls has raised contention as to its role in intestinal disease. Such findings could argue against the role of C. concisus in intestinal disease, however, the fact that C. concisus strains are genetically diverse raises the possibility that differences exist in their pathogenic potential. Evidence to support this view comes from studies showing strain specific differences in the ability of C. concisus to attach to and invade cells and produce virulence factors, including toxins and hemolytic phospholipase A. Further, sequencing of the genome of a C. concisus strain isolated from a child with CD (UNSWCD) and comparison of this with the only other fully sequenced strain (BAA-1457) would suggest that major differences exist in the genetic make-up of this species which could explain different outcomes of C. concisus infection.

Keywords: Campylobacter concisus; Crohn’s disease; antibiotic susceptibility; enteritis; intestine; oral; pathogenesis; reservoirs of infection.

Figure 1

Host attachment and invasion by Campylobacter concisus UNSWCD (adapted from Man et al., 2010a). Caco-2 cells were infected with bacteria at a MOI of 200 for 6 h. (A) The polar flagellum of C. concisus UNSWCD mediated attachment to the microvillus tip (triangles). (B) The flagellum appears to fold around the microvillus (triangle). (C) C. concisus induced a membrane ruffling-like effect (*). (D) C. concisus is observed half internalized in the host cell, resulting in a surface protrusion on the host cell membrane, and the flagellated half remains externally exposed. A host cell infected with multiple bacteria displays cell membrane irregularities and uneven texture because of bacteria-induced protrusions (arrows).

Figure 2

Preferential attachment of Campylobacter concisus UNSWCD to intercellular junctional spaces of host cells (adapted from Man et al., 2010a). HT-29 cells were infected with bacteria at a MOI of 200 for 6 h. (A–D) C. concisus UNSWCD preferentially attached to areas resembling the intercellular junctional space.