CAMPYLOBACTER CONCISUS

Campylobacter Concisus



Campylobacter Concisus

Introduction

Campylobacter concisus, a fastidious and slow-growing Gram-negative bacillus found in the human oral cavity, was first described in 1981. The species has been isolated in higher proportions from relatively shallow and healthy oral sites, suggesting that C. concisus is an oral commensal rather than a clinically significant oral pathogen. In addition, C. concisus can be isolated from the faeces of patients with diarrhoea, as well as from healthy individuals. Therefore, the possible role of C. concisus as a gastrointestinal pathogen has not yet been established firmly (Baker, 2006, 22).

In contrast to the well-known human pathogens Campylobacter jejuni, Campylobacter coli, Campylobacter lari and Campylobacter upsaliensis, C. concisus has no known animal hosts, suggesting that C. concisus is highly adapted to the human gastrointestinal tract. Inter-personal spread may be an important route of transmission, but is regarded as a relatively uncommon phenomenon for thermophilic Campylobacter spp. In a previous study, differences were observed in the age distribution of C. concisus patients, compared to the age distribution of patients with C. jejuni/C. coli infections. Most isolates were from the very young or elderly, indicating that C. concisus is an opportunistic pathogen for patients with immature or compromised immune systems. Bull et al., (2006, 645) explains “C. concisus is a genotypically heterogeneous species, and this may explain the conflicting reports of its pathogenic potential. Multiple genomospecies within the species have been described”.

Several potential virulence factors have been proposed for Campylobacter spp., including flagella-mediated motility, adhesion to intestinal mucosa, invasion of the epithelial cells of the intestine, and the ability to translocate and to produce toxin. However, the specific virulence mechanisms of Campylobacter spp. have not yet been elucidated adequately (Colles, 2008, 2042). The cytolethal distending toxin (CDT) is the most characterised of the Campylobacter toxins, and is encoded by the three adjacent genes cdtA, cdtB and cdtC in C. jejuni. The function of CDT in Campylobacter pathogenesis is unknown, but it has been shown that C. jejuni CDT causes sensitive cells to be blocked in the G2 phase of their cell cycle.

Bacterial strains

Thirty-nine C. concisus isolates from Danish patients with diarrhoea, and three from healthy individuals, were studied by Goode (2003, 5032), all the C. concisus isolates were collected during a previous study of the prevalence of campylobacters and related organisms in faeces. Five of the C. concisus-positive clinical cases were coinfected with an established bacterial enteric pathogen (three with Salmonella enterica subsp. enterica serovar Enteritidis, one with Shigella sonnei, and one with Yersinia enterocolitica). No patients or healthy individuals were related epidemiologically Goode, 2003, 5034). The C. concisus type strain CCUG 13144 was included in all assays, and the identity of the clinical isolates was reconfirmed by including the type strains of Campylobacter mucosalis, C. upsaliensis and C. concisus on all protein profiling gels. Growth conditions were as described below.

Phenotypic analysis

CDT-like activity by Vero cell assay

Bacterial cell-free supernatants and Vero cells were prepared as described previously with modifications. Campylobacter cell-free filtrate (50 µL) was added in duplicate at the desired ...