Downloaded from www.microbiologyresearch.org by IP: 54.70.40.11 On: Thu, 25 Oct 2018 21:45:54 Investigation of the effects of pH and bile on the growth of oral Campylobacter concisus strains isolated from patients with inflammatory bowel disease and controls Rena Ma, 1 Nicholas Sapwell, 1 Heung Kit Leslie Chung, 1 Hoyul Lee, 1 Vikneswari Mahendran, 1 Rupert W. Leong, 2 Stephen M. Riordan, 3 Michael C. Grimm 4 and Li Zhang 1 Correspondence Li Zhang L.Zhang@unsw.edu.au Received 10 December 2014 Accepted 17 December 2014 1 School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia 2 Concord Hospital, Sydney, University of New South Wales, Sydney 2052, Australia 3 Gastrointestinal and Liver Unit, Prince of Wales Hospital, Sydney, NSW 2052, Australia 4 St George and Sutherland Clinical School, University of New South Wales, Sydney, NSW 2052, Australia Campylobacter concisus is an oral bacterium that is associated with inflammatory bowel disease (IBD). This study examined the impact of pH and bile on the growth of oral C. concisus strains isolated from patients with IBD and controls. The growth of 58 C. concisus strains on horse blood agar (HBA) plates following exposure to media with various pH values for different time points was examined. Furthermore, the growth of C. concisus strains on HBA plates containing different concentrations of ox bile was investigated. Following exposure to pH 2 for 30 min, none of the 58 oral C. concisus strains grew on HBA plates. Following exposure to pH 3.5 for 30 min, only four of 20 oral strains examined grew on HBA plates, with a log 10 c.f.u. reduction of 0.7–2.5 compared to the same strains without low pH exposure. Exposure to pH 5 for 120 min had minimal effects on C. concisus growth. Approximately half of the oral strains (55.2 %, 32/58) grew on HBA containing 2 % bile. Bile inhibited the growth of C. concisus in a dose- and strain- dependent manner. These data suggest that both bacterial and intestinal environmental factors may play a role in the determination of C. concisus colonization in the different parts of the gastrointestinal tract and that increased gastric pH and reduced intestinal bile may be risk factors for increased gastric and intestinal C. concisus colonization. INTRODUCTION Campylobacter concisus is a Gram-negative bacterium of the human oral cavity (Tanner et al., 1981; Zhang et al., 2010). C. concisus has been shown to be associated with inflammatory bowel disease (IBD). IBD is the chronic inflammation of the gastrointestinal tract and it usually manifests as either Crohn’s disease (CD) or ulcerative colitis (UC) (Cosnes et al., 2011). A significantly higher prevalence of C. concisus was detected using PCR in both the intestinal biopsies and faecal samples collected from patients with IBD as compared to controls (Mahendran et al., 2011; Man et al., 2010; Mukhopadhya et al., 2011; Zhang et al., 2009). In addition to IBD, C. concisus has also been associated with diarrhoeal disease, being frequently isolated from diarrhoeal faecal samples (Engberg et al., 2000; Lastovica, 2009; Nielsen et al., 2013). C. concisus was previously isolated from the saliva samples of nearly all people tested (Zhang et al., 2010). However, in healthy individuals, intestinal colonization by C. concisus is rare. Previous studies have reported that the isolation rate of C. concisus from faecal samples is low, having been isolated from only 3 % (3/107) of healthy individuals (Engberg et al., 2000) and from no (0 of 108) healthy individuals at all (Nielsen et al., 2013). C. concisus strains isolated from intestinal biopsies of patients with IBD were genetically identical or closely related to oral C. concisus strains isolated from the same or other patients, suggesting that C. concisus strains that colonize the human intestinal tract originate from oral C. concisus strains (Ismail et al. 2012). Abbreviations: CD, Crohn’s disease; IBD, inflammatory bowel disease; UC, ulcerative colitis. Journal of Medical Microbiology (2015), 64, 438–445 DOI 10.1099/jmm.0.000013 438 000013 G 2015 The Authors Printed in Great Britain