Introduction

B. hominis  is an inhabitant of the human intestinal tract.  It is capable of both sexual and asexual      reproduction by binary fission and of pseudopod extension and retraction.  

Morphology

The classic form that is usually seen in stool specimens varies in size from 6 - 40 microns and is characterised by a large membrane bound central body which occupies 90% of the cell.  It has no internal nuclear structure and a rim of peripheral granules the function of which is not known.

Clinical disease

The pathogenic potential of B. hominis is unclear, though this organism has been associated with nausea, fever, vomiting, diarrhoea and abdominal pain.

Diagnosis

Permanently stained preparations of faecal smears is the procedure of choice for identification, although the organism can be seen in wet preparations. The recommended stains are Fields' and Giemsa.

A trophozoite of Blastocystis hominis exhibiting the thickened cell wall and a nucleus.