Downloaded from www.microbiologyresearch.org by IP: 54.70.40.11 On: Thu, 06 Dec 2018 15:15:18 Review Campylobacter–Acanthamoeba interactions Ana Vieira, Alan M. Seddon and Andrey V. Karlyshev Correspondence Andrey Karlyshev a.karlyshev@kingston.ac.uk Received 16 December 2014 Accepted 9 March 2015 Faculty of Science, Engineering and Computing, Kingston University, Penrhyn Road, Kingston upon Thames, Surrey KT1 2EE, UK Campylobacter jejuni is a foodborne pathogen recognized as the major cause of human bacterial enteritis. Undercooked poultry products and contaminated water are considered as the most important sources of infection. Some studies suggest transmission and survival of this bacterial pathogen may be assisted by the free-living protozoa Acanthamoeba. The latter is known to play the role of a host for various pathogenic bacteria, protecting them from harsh environmental conditions. Importantly, there is a similarity between the mechanisms of bacterial survival within amoebae and macrophages, making the former a convenient tool for the investigation of the survival of pathogenic bacteria in the environment. However, the molecular mechanisms involved in the interaction between Campylobacter and Acanthamoeba are not well understood. Whilst some studies suggest the ability of C. jejuni to survive within the protozoa, the other reports support an extracellular mode of survival only. In this review, we focus on the studies investigating the interaction between Campylobacter and Acanthamoeba, address some reasons for the contradictory results, and discuss possible implications of these results for epidemiology. Additionally, as the molecular mechanisms involved remain unknown, we also suggest possible factors that may be involved in this process. Deciphering the molecular mechanisms of pathogen– protozoa interaction will assist in a better understanding of Campylobacter lifestyle and in the development of novel antibacterial drugs. Introduction Free-living protozoa, such as amoebae, are widespread in nature. They have been isolated from a wide variety of public water supplies, swimming pools, bottled water, ventilation ducts, soil, surgical instruments and contact lenses (Sandstro ¨m et al., 2011). Amoebae are the dominant bacterial consumers, contributing to recycling of nutrients and maintaining the structure of the microbial community (Greub & Raoult, 2004). These micro-organisms have been the subject of intensive investigation due to their ability to capture prey by phagocytosis, act as vectors and hosts for pathogenic organisms, and their ability to produce serious human infections (Siddiqui & Khan, 2012a). Campylobacter bacteria, known to be the most important enteric pathogen, are sensitive to environmental stress outside their warm-blooded hosts (Park, 2002). It was reported that amoebae may act as a protective envir- onmental host for this pathogen; thus, creating a problem for human and animal health. However, there are varying accounts in the literature on the types of interaction between Campylobacter and Acanthamoeba. In this review, we perform critical analysis of these data and discuss possible reasons for the conflicting results. We also indicate Campylobacter factors that may be involved in the interaction of this pathogen with amoeba. Elucidation of the molecular mechanisms of Campylobacter–Acanthamoeba interaction is important for public health, since foodborne pathogens and amoebae co-occur in the same environments (Vaerewijck et al., 2014). Acanthamoeba Acanthamoeba is a genus of amoebae that includes free- living protozoan pathogens commonly found in soil and water and characterized by spine-like structures on their surface, known as acanthopodia. They contain one or more contractile vacuoles, whose function is to expel water for osmotic regulation, digestive vacuoles, lysosomes and glycogen-containing vacuoles (Siddiqui & Khan, 2012c). Acanthamoebae have two stages in their life cycle: an active trophozoite stage, in which they exhibit vegetative growth when the cells divide mitotically and when they feed on organic particles and microbes; and a dormant double- walled cyst stage with minimal metabolic activity, which amoebae adopt when under harsh environmental condi- tions (Siddiqui & Khan, 2012c). Although the trophozoites are the infective forms, both amoebal forms can enter the human host through a variety of routes, including the eyes, causing severe blinding keratitis, and also through nasal passages or skin lesions, from where they may further Abbreviations: CDT, cytolethal distending toxin; CPS, capsular polysaccharide; LOS, lipooligosacharides. Microbiology (2015), 161, 933–947 DOI 10.1099/mic.0.000075 000075 G 2015 The Authors Printed in Great Britain 933