Page 289 - parasitology for medical and clinical laboratoryprofessionals

Laboratory Procedures for Identifying Parasitic Organisms and Their Ova 269

Yeast Bodies
1. Float in almost all commonly used flotation solutions.

2. Similar to Giardia in size, shape, and color but may be mistaken for red blood
cells, except for greenish-gray cast. Yeast bodies are often more common than
Giardia.
3. Contains circular vacuoles, but no body structures such as axonemes, nuclei, or
median bodies are visible.
4. If yeasts are actively growing, buds can form on the yeast bodies.

Sarcocystis spp. and Cryptosporidium sp.
1. Sarcocystis spp. sporocysts are about the same size as Giardia cysts. They

float in all commonly used flotation solutions. Their internal structure consists
of four banana-shaped sporozoites and a clump of material called a residium.
Because of its relatively thicker cyst wall, Sarcocystis is more easily seen
than Giardia.
2. Cryptosporidium sp. is spherical and measures 3 to 5 μm in diameter. They are
so small that they are often missed during the fecal examination.

Other Considerations
1. Oocysts of Isospora belli are lightweight and may float near the top of the

meniscus.
2. A phase-contrast microscope may be used to determine the presence of
Cryptosporidium, Cyclospora, and Isospora.
3. Centrifugation may distort the helminths eggs that are thin-shelled and some
protozoan cysts.
4. It may be important to examine the sediment following the flotation method,

because the heavier operculated eggs and the unfertilized A. lumbricoides eggs
do not float.

Results and Report for Flotation Procedures
Any parasites observed should be reported by both genus and species if possible,
using the characteristics in the descriptions listed previously. The stages exhibited
by the parasite (ova, larvae, cyst, trophozoite) are important clinical items leading to
appropriate treatment for the victim of the infection. Cellular components such as
RBCs, WBCs, yeast, etc., are reported in a semiquantitative form, as few, moderate, or
many. Charcot-Leyden crystals are also reported semiquantitatively. Any other iden-
tifiable elements such as artifacts or undigested materials may provide clues as to a

medical condition requiring treatment.