Acanthamoeba from human nasal mucosa infected with an obligate intracellular parasite

Abstract

Summary An aggregation of numerous round particles could be observed inside the cytoplasm of trophozoites of an Acanthamoeba strain (Bn 9 ) isolated from human nasal mucosa [8]. Transmission and scanning electron microscopy revealed small coccoidal bacteria (0.4–0.6 μm in diameter) with a prominent trilamellar cell wall. Initially the bacteria multiplied inside food vacuoles of infected trophozoites, later on they could also be observed free in the cytoplasm. The affected host cells were finally ruptured liberating the bacteria into the environment. The procaryotes were ingested by further trophozoites that were not able to digest them but became lethally infected, too. The parasitic bacteria were successfully transfered to a pathogenic A. castellanii strain (C 3 ). Infected amoebae could be cured from parasites by rifampicin. The taxonomic position of the gram-positive cocci could not be determined. So far it was not possible to subcultivate the organisms in vitro. Therefore we assume that they are obligate intracellular parasites of amoebae, comparable to those rod-shaped bacteria described by Drozanski [3] as obligate pathogens of Acanthamoebae.