Genetic Factors of Required for Its Interactions with Free-Living Amoeba.

, a free-living amoeba ubiquitous in environmental water, has been considered as the environmental reservoir of certain bacterial pathogens, including , an intracellular human pathogen causing self-limiting gastroenteritis. - interaction mechanisms may help clarify how the otherwise fastidious bacterium survives in environmental waters. In this study, we constructed single deletion mutants of strain 81-176 for the 10 selected genes (, , , , , , , , , and ) previously shown to be important for the interaction (invasion and intracellular survival) of with mammalian hosts. We used a modified gentamicin protection assay to quantify the internalization and intracellular survival of these mutants and the wild type with the two species of ( and ). Both internalization and intracellular survival were significantly lower for all mutants compared to the wild type with both amoeba strains, except for in the internalization assay with ( < 0.05). The results of this study highlight that the mechanisms used by to interact with mammalian hosts are conserved in its interactions with amoeba hosts. This understanding may be useful in developing effective strategies to reduce the transmission of to chickens through drinking water.