Filamoeba sp. Isolated from Hot-water Piping System, a Host of Legionella Closely Related to Legionella micdadei

An amoeba was isolated from 56C hot water, sampled in a piping system that was monitored for the presence of legionellae. The amoeba strain JIH56 was derived from the primary isolate by subculturing at 38C. It was assigned to the genus Filamoeba Page, 1967 using light microscopical, ultrastructural and molecular criteria. In the cytoplasm of Filamoeba trophozoites were found Legionella-like bacteria. These were determined using Legionella-specific PCR assay followed by sequencing. Phylogenetic analysis and a similarity search revealed a close relationship of the newly determined legionella sequence with sequences of Legionella micdadei (syn. Tatlockia micdadei), the Pittsburgh pneumonia agent. Phylogenetic analysis of the Filamoeba sequences available to date suggests that the ATCC 50430 strain was misidentified.