Campylobacter is the most common bacterial cause of enteric disease worldwide , with an average of ten thousand Canadian and two million American cases reported annually [2, 3]. Within the Campylobacter genus, C. jejuni, and its close relative C. coli, are reported as the most common cause of human acute bacterial enteritis. However, there is mounting evidence that other members of this genus, including C. upsaliensis, C. concisus, C. gracilis, C. rectus and C. showae, are under-appreciated for the part they play in enteritis, as well as other disease presentations [4–7]. With foodborne contamination the most recognized source for infections, ingestion of untreated water, raw milk, undercooked chicken and the cross-contamination of foods are recognized risk factors for acquiring Campylobacter [8–11]. In addition, many natural animal reservoirs for Campylobacter have been recognized, which include chicken and other poultry, wild birds, pigs, dogs, cats, sheep and cows . Studies from the United States, Sweden and Australia all identify ownership of a pet dog as a risk factor for Campylobacter infections, especially among infants and small children [8–10]. Despite this fact, our knowledge of Campylobacter ecology in dogs is quite limited.
Research carried out in Europe and Asia has begun to address this question with various culture-based studies. Researchers from Taiwan, Finland, Sweden, Demark and the Netherlands have examined various dog populations and have been able to culture C. jejuni, C. coli, C. upsaliensis, C. helveticus, C. lari and other Campylobacter spp. from canine fecal samples using various growth conditions and media [13–17]. Reported carriage rates of Campylobacter spp. in domestic dogs ranged from 2.7% to 100% of dogs tested [13, 16], with some studies reporting isolation of multiple species of Campylobacter from a single dog [15, 17].
A major influence on our understanding of Campylobacter ecology in dogs has been our reliance on culture-based methods. Various selective media have been used for Campylobacter isolation , with most relying on a cocktail of antibiotics in a rich basal medium to selectively isolate Campylobacter. However, it has been recognized that Campylobacter species other than C. coli, C. jejuni, and C. lari are often sensitive to the antibiotics in these media . Filter-based methods, in combination with nonselective media, have been shown to result in the isolation of a greater diversity of Campylobacter species , but these approaches are more labour-intensive, less selective and prone to overgrowth of fecal contaminants . As our understanding of campylobacters, both pathogenic and non-pathogenic, expands beyond C. jejuni and C. coli, so must our detection methods.
The goal of this study was to take a culture-independent approach to the profiling of Campylobacter species in domestic pet dogs in an effort to evaluate this zoonotic reservoir and describe changes in fecal Campylobacter populations associated with diarrhea. Established species-specific quantitative PCR (qPCR) assays targeting the 60 kDa chaperonin (cpn60) gene of C. coli, C. concisus, C. curvus, C. fetus, C. gracilis, C. helveticus, C. hyointestinalis, C. jejuni, C. lari, C. mucosalis, C. rectus, C. showae, C. sputorum, and C. upsaliensis  were used to determine the Campylobacter profiles of 70 healthy dogs and 65 dogs with diarrhea. This study represents the largest culture-independent, quantitative investigation of Campylobacter in pet dogs conducted to date and is one of only a few studies to focus on North American animals.