Influence of temperature, oxygen and bacterial strain identity on the association of Campylobacter jejuni with Acanthamoeba castellanii

Campylobacteriosis is the most frequently reported foodborne disease in the industrialized world, mainly through consumption of contaminated chicken meat. To date, no information is available on the primary infection sources of poultry. In this study, the ability of five Campylobacter jejuni strains with different invasion potential towards Caco-2 cells to survive and replicate in the protozoan Acanthamoeba castellanii was tested under simulated in situ conditions (i.e. chicken broiler houses). Results indicate that environmental conditions play a crucial role in C. jejuni-A. castellanii interactions. Co-culture in general did not result in an increase of either bacteria or amoebae. However, co-culture with Acanthamoeba did result in a delayed decline and an increased long-term survival of Campylobacter. Bacterial strain-specific effects were observed, with higher survival rates for low-invasive strains. The presence of C. jejuni in general did not affect A. castellanii viability, except at 37 degrees C under microaerobic conditions, where the presence of the reference and low-invasive Campylobacter strains resulted in a significant decline in amoebal viability. Confocal laser scanning microscopy revealed that intra-amoebal campylobacters were not always colocated with acidic organelles, suggesting potential bacterial interference with digestive processes. As Acanthamoeba enhances the persistence of C. jejuni, the presence of the amoeba in broiler house environments may have important implications for the ecology and epidemiology of this food pathogen.