ABSTRACT
The three conditions required for a microorganism to produce disease, i.e., commun-icability, invasiveness, and pathogenicity can be fulfilled with great efficiency by pathogenic strains of the protozoan parasite Entamoeba histolytica. The electrophysiological measurement of transepithelial changes was, by far, the most sensitive method for the detection of early membrane changes produced by the parasite, since sizeable decreases can be recorded only 2 minutes after the addition of living trophozoites. Trophozoite adhesion to human red blood cells is an active process that depends on both the cytoskeleton and metabolic energy of amebas and on the mobility of amebic and erythrocyte surface ligands. Lysis is also blocked by calcium-channel blockers, suggesting that calcium fluxes in the ameba and entry of calcium into the target cell are involved in the cytopathic effect.
