ISOLATION OF AN AMEBA NATURALLY HARBORING A DISTINCTIVE LEGIONELLA SPECIES

There are numerous in vitro studies documenting the multiplication of Legionella species in free-living amoebae and other protozoa. It is be lieved that protozoa serve as host cells for the intracellular replica tion of certain Legionella species in a variety of environmental setti ngs. This study describes the isolation and characterization of a bact erium initially observed within an amoeba taken from a soil sample. In the laboratory, the bacterium multiplied within and was highly pathog enic for Acanthamoeba polyphaga. Extracellular multiplication was obse rved on buffered charcoal yeast extract agar but not on a variety of c onventional laboratory media. A 16S rRNA gene analysis placed the bact erium within the genus Legionella, Serological studies indicate that i t is distinct from previously described species of the genus. This rep ort also describes methods that should prove useful for the isolation and characterization of additional Legionella-like bacteria from free- living amoebae. In addition, the characterization of bacterial pathoge ns of amoebae has significant implications for understanding the ecolo gy and identification of other unrecognized bacterial pathogens.