Free-living amoebae may serve as hosts for the Chlamydia-like bacterium Waddlia chondrophila isolated from an aborted bovine foetus

Chlamydia-like endocytobionts are commonly observed in protozoan hosts. Therefore, we examined the potential of 21 different species of free-living amoebas to serve as hosts of a newly found bacterium, Waddlia chondrophila. The Chlamydia-like bacterium Waddlia chondrophila 2032/99 was originally isolated from an aborted bovine foetus in Rheinstetten, Germany. The inoculum of the obligate intracellular agent was prepared from Buffalo Green Monkey (BGM) cells. The infection of Hartmannella vermiformis OS101 revealed typical morphological stages of a Chlamydia-like life cycle, including the presence of elementary and reticulate bodies. The following infection studies with a Hartmannella-adapted Waddlia isolate showed that also Acanthamoeba sp. Gr. II HLA, Vahlkampfia ovis Rhodos, H. vermiformis C3/8, Hyperamoeba-like amoeba B1,2-100PE and Dictyostelium discoideum So-P2 supported the growth of Waddlia. An interesting finding was that Hartmannella-adapted Waddlia exhibited a broader host range when compared to the BGM cell isolate. The concept that Waddlia may fall into the group of environmentally preadapted pathogens is discussed.