A better understanding of these mechanisms

is required in order to facilitate the development of appropriate intervention strategies to reduce the burden of C. jejuni-associated diseases [13]. Aquatic environments are reservoirs for C. jejuni[7, 14, 15] and contaminated drinking water has been implicated in several C. jejuni outbreaks [16–18]. Acanthamoeba spp. are free-living amoebae which can be found widely in water [19–21]. They have evolved efficient mechanisms to phagocytose and kill bacteria that they use as a source of nutrients BAY 11-7082 in vitro [22, 23]. However, the relationship of amoeba with bacteria can be complex. We and others have indicated that amoebae can promote the survival of C. jejuni[24–28] and our study specifically showed that the bulk of this growth was extracellular. We also showed that while the majority of internalized C. jejuni does not survive ingestion by A. castellanii

beyond 5 h, a very small number of bacterial cells are able to survive intracellularly and are thereby protected from external disinfectant killing during this time frame [27]. During this period, chicks may still get contaminated by Campylobacter from infected amoebae present in the water source, as it has been reported that intra-amoeba Campylobacter can colonize broiler chickens and may represent a significant environmental source of transmission [29]. Although the mechanisms of survival of C. jejuni outside the host are not fully understood, it has been proposed that stress-adapted C. jejuni can survive environmental stresses better than non-stressed cells Combretastatin A4 [10, 30]. Likewise, pre-exposure to stress may affect the interaction of stressed C. jejuni cells with Mirabegron amoeba. To date, little is known about the interaction of stressed C. jejuni

and A. castellanii, but this needs to be investigated as both of these organisms occupy a check details similar ecological habitat [21, 31, 32]. The importance of the interplay between C. jejuni and amoeba under stress conditions was recently highlighted by the fact that co-incubation with amoeba increases acid tolerance and survival of C. jejuni[24, 26, 27, 33]. Therefore, the interactions between C. jejuni and Acanthamoeba are relevant to the transmission of C. jejuni from the environment to new hosts. Several genes and the encoded proteins have been shown to be important for C. jejuni to adapt to environmental changes and to facilitate its interactions with eukaryotic cells. Examples of potential relevance to this study are the CiaB protein, which enhances invasion of eukaryotic cells [34, 35], and the HtrA protein that degrades and prevents aggregation of periplasmic proteins that misfold during stress [36, 37]. Another example is DnaJ, which aids in protein folding and plays a role in C. jejuni thermotolerance and in chicken colonization [11, 38]. Transcription of dnaJ is up-regulated upon temperature stress [12].