The Journal of Medical Microbiology, Vol 12, Issue 3 355-362, Copyright © 1979 by Society for General Microbiology
Inhibition by amoeba-specific antiserum and by cytochalasin B of the cytopathogenicity of Naegleria fowleri in mouse embryo-cell cultures
T. Brown
Inhibitors of trophozoite motility and phagocytosis were used to
investigate the mechanism of Naegleria fowleri cytopathogenicity in
mouse-embryo (ME)-cell cultures. Amoebae that were immobilised and
agglutinated by specific antiserum exhibited no cytopathic activity,
although they remained alive and were in constant contact with the ME
cells. Mammalian-cell damage occurred only when the organisms recovered
pseudopodium function and began to migrate over the monolayers as they
overcame the inhibitory effects of the antiserum. Cytochalasin B at a
concentration of 10 microgram/ml, shown to prevent the engulfment of chick
erythrocytes by amoebae, also inhibited the cytopathogenicity of Naegleria
when incorporated in ME-cell culture medium. Despite repeated contact with
active trophozoites, the ME cells showed only those morphological changes
characteristically induced by cytochalasin B itself. The amoebae in turn
showed signs of starvation after 3 or 4 days' incubation, suggesting that
the feeding activity of trophozoites was suppressed. Colchicine, on the
other hand, inhibited neither the ingestion of erythrocytes nor the
destruction of ME cells by amoebae. It was concluded that the
cytopathogenicity of N. fowleri in ME-cell cultures was due to physical
rather than biochemical or cytotoxic mechanisms and was associated with the
phagocytic activity of trophozoites.
