[Staining of cysts of Entamoeba invadens, Entamoeba histolytica and Entamoeba coli with wheat germ agglutinin labelled with colloidal gold].

Cysts of Entamoeba invadens obtained under axenic conditions were stained with wheat germ agglutinin labelled with colloidal gold. Microscopic observation of encysting cultures revealed that upon staining, cysts acquired a red coloration, while trophozoites remained unstained. E. histolytica and E. coli cysts obtained from asymptomatic patients were also stained red by this technique. Electronmicroscopic examination of stained cells showed a layer of colloidal gold granules attached to the surface of cysts, while trophozoites remained free of gold granules. The results of the staining procedure developed, agreed with the known facts that wheat germ agglutinin is a lectin that binds specifically to chitin and its oligomers, and that chitin is present in the cyst wall of E. invadens. The results suggested that chitin is also present in the wall of cysts of E. histolytica and E. coli.