Free-living Amoebae Serve as a Host for the Chlamydia-like Bacterium Simkania negevensis

Institut fur Medizinische Mikrobiologie des Klinikums, Jena, GermanySummary. Members of the novel family Parachlamydiaceae are commonly observed in free-living amoebae (FLA) as host cells. Therefore,we examined the potential of 14 different species of free-living amoebae to serve as hosts of the Chlamydia-like bacterium, Simkanianegevensis, previously isolated as a contaminant from a cell culture in Israel (Kahane et al. 1993, 1995). The inoculum of the obligateintracellular agent was prepared from Buffalo Green Monkey (BGM) cells. The infection of Acanthamoeba strain HLA and of Naegleriaclarki (N-DMLGo) revealed typical morphological stages of a Chlamydia-like life cycle, including the presence of elementary and reticulatebodies, as could be shown by electron microscopy. Subsequent infection studies with an Acanthamoeba-adapted Simkania isolate showedthat also Balamuthia mandrillaris and one of two Hartmannella strains supported the growth of Simkania. Balamuthia can be consideredas an experimental host for mass production of elementary bodies. This is based on the finding that the host amoebae expelled g reat numbersof bacteria leading to a long-term survival of the infected trophozoites. The observation that Simkania negevensis can survive and replicatewithin at least four of tested FLA species suggests that various free-living amoebae may serve as survival and multiplication vehiclessupporting the spread of these pathogens in aquatic environments. The concept that Simkania may fall into the group of environmentallypreadapted pathogens is discussed as well.Key words: Acanthamoeba, Balamuthia, Chlamydia, endoparasite, Hartmannella, host range, Neochlamydia, Simkania negevensis,ultrastructure, Waddlia.