Manual of basic techniques for a health laboratory - libdoc.who.int

114 Manual of basic techniques for a health laboratoryTable 4.4 Features for the differential diagnosis of Entamoeba histolytica and E. coliFeature E. histolytica E. coliMotion In a definite direction HaphazardMotility Fairly motile Non-motile or barely motileEctoplasm Transparent, quite different from Little or no differentiation fromendoplasmendoplasmInclusion bodies Erythrocytes if haematophagous Bacteria, yeast cells and varied debris,no erythrocytesNucleus (fresh state) Invisible Visible (nuclear membrane is like abead necklace)Nuclear membrane (after staining Regular membrane Irregular membranewith iodine solution)Karyosome Small, dense, central Large, eccentricFig. 4.16 EntamoebahartmannitrophozoiteNucleus: visible in the fresh state, without staining. The membrane is irregular andgranular (like a bead necklace), the karyosome large and eccentric.Table 4.4 summarizes the features used for the differential diagnosis of Entamoebahistolytica and E. coli. If a trophozoite moves quickly in one direction and projectspseudopodia rapidly, it is probably Entamoeba histolytica. Other species of amoebado not usually move like this. If the trophozoite moves as described and if erythrocytesare present in the cytoplasm, it can be assumed that it is E. histolytica. If necessary,buffered methylene blue can be used to stain the nucleus for confirmation.Entamoeba hartmanni (Fig. 4.16)Size: always less than 10mm (about the size of an erythrocyte).All characteristics similar to those of E. histolytica but never contains erythrocytes.There may be distinct vacuoles.Fig. 4.17 Endolimax nanustrophozoiteEndolimax nanus (Fig. 4.17)Size: 6–10mm.Motility: many small rounded pseudopodia moving slowly in all directions.Cytoplasm: very granular with small vacuoles.Inclusion bodies: various (mainly bacteria).Nucleus: karyosome similar to an ink-spot, visible after staining with iodine solution.Fig. 4.18 IodamoebabutschliitrophozoiteIodamoeba butschlii (Fig. 4.18)Size: 10–15mm.Shape: compact, leaf-like.Motility: very slow; clear, rounded or finger-shaped pseudopodia.Inclusion bodies: bacteria, large vacuoles.Nucleus: a large oval karyosome next to a group of granules, visible after stainingwith iodine solution.I. butschlii amoebae are rarely seen in stools.Fig. 4.19 Dientamoebafragilis trophozoiteDientamoeba fragilis (Fig. 4.19)Size: 6–15mm.Shape: round.