Study of a Small Amoeba from Mammalian Cell Cultures Infected with "Ryan Virus'

Abstract

SUMMARY: A small amoeboid organism, found in mammalian tissue cultures inoculated with an infective agent formerly termed ‘Ryan virus’, is shown to have the morphological, cultural and behavioural characters of the free-living soil amoeba Hartmannella castellanii Douglas, 1930. Cytopathic changes occurred regularly in the infected monolayers; this was evidently due to action of the amoebae rather than the presence of any associated bacterial or viral agents. Strong circumstantial evidence suggests that the Ryan isolates of H. castellanii originated, either as trophozoites or cysts, from swabs of the human nasopharynx. Recovery of hartmannellid amoebae from this source is of interest in relation to some recently reported cases of pyogenic meningitis, apparently caused by free-living soil amoebae.