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Morphology, histochemistry and infectivity of Blastocystis hominis cyst
1Department of Parasitology, Faculty of Medicine, Alexandria University, Egypt.
Abstract:
Different morphological forms of Blastocystis hominis had been identified in human stool samples. These included both cystic and trophic stages. The latter was induced to encyst by keeping them in potassium dichromate solution for two weeks. Suspected of being the infective stage, cysts were studied in more detail as regards their morphology using both light and electron microscopy. Histochemistry and infectivity studies were also carried out. Light microscopy revealed the cysts to be ovoid or round 5-7 microm with thick cyst wall and a single nucleus. The induced cysts were morphologically similar to the cysts present in the stool. By electron microscope, the cyst wall was evident surrounded by an additional fibrillar coat. The cytoplasm contained one nucleus, many mitochondria, glycogen deposits and a number of variable sized vacuoles. Histochemical studies detected carbohydrates in the cyst wall and fat globules in the cytoplasm. Oral inoculation of albino mice with these cysts led to inflammatory changes in the large and small intestine. The parasite was found at the mucosal epithelium but with no invasion. Different forms of the parasite were detected in the lumen of the intestine.
Insights
Blastocystis hominis cysts, the suspected infective stage, were characterized using microscopy and histochemistry. Oral inoculation in mice caused intestinal inflammation, confirming their role in Blastocystis infections.
Area of Science:
- Parasitology
- Microbiology
- Cell Biology
Background:
- Blastocystis hominis is a common intestinal parasite found in humans.
- Morphological variations, including cystic and trophic stages, have been observed.
- The infective stage of Blastocystis hominis has been a subject of investigation.
Purpose of the Study:
- To characterize the morphology of Blastocystis hominis cysts.
- To investigate the infectivity of Blastocystis hominis cysts in a murine model.
Main Methods:
- Induction of cyst formation in vitro using potassium dichromate solution.
- Morphological analysis using light and electron microscopy.
- Histochemical staining for carbohydrates and fats.
- Infectivity studies involving oral inoculation of albino mice.
Main Results:
- Cysts were ovoid/round (5-7 microm) with a thick wall and single nucleus, confirmed by light and electron microscopy.
- Electron microscopy revealed a fibrillar coat around the cyst wall and cytoplasmic components like mitochondria and glycogen.
- Histochemistry detected carbohydrates in the cyst wall and fat globules in the cytoplasm.
- Mouse inoculation led to intestinal inflammation and parasite presence at the mucosal epithelium without invasion.
Conclusions:
- The induced cysts are morphologically similar to those found in human stool.
- Blastocystis hominis cysts possess distinct ultrastructural and biochemical features.
- These cysts are capable of inducing inflammatory responses in the host intestine, supporting their role as the infective stage.
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