High power detail of E. histolytica trophozoites with eritrocytes inside.

The degree of virulence of cultured E. histolytica varies
according to the strain and culture condition The factors
responsible for these variations remain obscure. Despite a
large amount of information on the subject, ultrastructural
and biochemical studies have not been able to demonstrate
differences that could explain the variable degree of
virulence. Certain cell surface properties appear to
characterize pathogenic strains: adhesion to epithelial cells)
, susceptibility to agglutinate with concanavalin A, ability to
produce lytic effect on cultured cells and phagocytosis
oferythrocytes. Recently, a correlation between
collagenase production and virulence has been found.