engleski

Cointeractions of Listeria monocytogenes and free-living amoeba Acanthamoeba castellanii

Listeria monocytogenes is gram - positive bacterium associated with potentially serious invasive diseases in humans and in a variety of animal species. Because of ubiquitous distribution in the environment, L. monocytogenes may be involved in the interactions with free-living protozoa, a common representative of natural ecosystems. We investigated the interactions of haemolytic L. monocytogenes (EGD strain) with the free-living amoeba, Acanthamoeba castellanii (ATCC 30234). Survival of bacteria and amoeba was checked at regular intervals, coupled with microscopy. At 22oC, as well as at 35oC, listeria was internalized into A. castellanii but was not able to establish an intracellular lifestyle within the eucaryotic host. It was shown, by gentamicin protection assays, that L. monocytogenes could be recovered by culture only four hours after coculture establishment. L. monocytogenes had no killing effect on the amoebae but did cause rapid protozoan encysment, probably thanks to LLO production. However, the presence of amoeba enhanced the growth of listeria according to higher numbers of extra cellular bacteria when cultured with amoebae compared with growth in their absence. Higher numbers were likely sustained on metabolic waste products released during coculture. Although free-living amoeba and listeria may be found in the same environment it seems that L. monocytogenes is not maintained nor transferred in the environment by association with Acanthamoeba castellanii. However, presence of acanthamoeba seems to be beneficial for microorganism and it could thus be speculated that such cointeraction is also important for L. monocytogenes survival in its natural environment.

Listeria monocytogenes; Acanthamoeba castellanii; coculture; survival

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