The presence in the intestine of amoebae species other than Entamoeba histolytica indicates faeco-oral transmission and the possible presence of pathogenic amoebae. For example, Entamoeba coli can be regarded as an organism indicating poor hygiene. It is apathogenic and is frequently confused with E. histolytica. Entamoeba coli trophozoites move slowly and never contain red blood cells, unlike the swift and haematophagous E. histolytica. Entamoeba coli cysts are larger (10-30 m m) and may contain up to eight nuclei. The cysts contain no chromatoid bodies. The morphology of Entamoeba histolytica and Entamoeba dispar is identical. In order to distinguish between the two, PCR technology is used. Entamoeba hartmanni is a non-pathogenic intraluminal parasite which can only be distinguished from E. histolytica forms by its smaller dimensions, and which was regarded as a non-pathogenic zymodeme of E. histolytica. Entamoeba gingivalis is an amoeba found as a trophozoite in the mouth and in the gingival sulci. No cyst stage is known and it does not occur in the intestine. Sometimes the amoeba is found in cervical smears. The parasite is transmitted by kissing and also by orogenital contact. It is usually regarded as a non-pathogenic commensal, but should be noted that some doubt the absence of its pathogenic capacity. Endolimax nana is apathogenic. The trophozoites move slowly. The cysts are oval, small (6-12 m m) and contain two to four nuclei. Here too there are no chromatoid bodies. Iodamoeba butschlii also has small cysts. These have only one nucleus and a glycogen mass which stains with iodine (Lugol), from which it gets its name. The amoeboflagellate Dientamoeba fragilis is a non-invasive parasite which may be the cause of undifferentiated diarrhoea. It is very difficult to demonstrate because the vegetative form is easily damaged (fragilis = breakable). No cyst stage is known and transmission via trophozoites can take place. One hypothesis as to how transmission is still possible, is that Enterobius vermicularis (pinworms) could function as vectors. If the faeces cannot be brought quickly to the laboratory (ideally < 10'), they should be fixed in PVA (polyvinyl alcohol) or SAF (sodium acetate formalin).