Environmental Mycobacterium avium subsp. paratuberculosis Hosted by Free-Living Amoebae

Ascel Samba-Louaka, Etienne Robino, Thierry Cochard, Maxime Branger, Vincent Delafont, Willy Aucher, Wilfrid Wambeke, John P. Bannantine, Franck Biet, Yann Héchard

Mycobacterium avium subsp.paratuberculosisis responsible for paratuberculosis in animals. This disease, leading to an inflammation of the gastrointestinal tract, has a high impact on animal health and an important economic burden. The environmental life cycle ofM. aviumsubsp.paratuberculosisis poorly understood and several studies suggest that free-living amoebae (FLA) might be a potential environmental host. FLA are protozoa found in water and soil that are described as reservoirs of pathogenic and non-pathogenic bacteria in the environment. Indeed, bacteria able to survive within these amoebae would survive phagocytosis from immune cells. In this study, we assessed thein vitrointeractions between several strains ofM. aviumsubsp.paratuberculosisandAcanthamoeba castellanii. The results indicate that the bacteria were able to grow within the amoeba and that they can survive for several days within their host. To explore the presence ofM. aviumsubsp.paratuberculosisin environmental amoebae, we sampled water from farms positive for paratuberculosis. AM. aviumsubsp.paratuberculosisstrain was detected within an environmental amoeba identified as related to the poorly describedRosculusgenus. The bacterial strain was genotyped, showing that it was similar to previous infectious strains isolated from cattle. In conclusion, we described that variousM. aviumsubsp.paratuberculosisstrains were able to grow within amoebae and that these bacteria could be found on farm within amoebae isolated from the cattle environment. It validates that infected amoebae might be a reservoir and vector for the transmission ofM. aviumsubsp.paratuberculosis.