[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

CHAPTER 12 Artifacts and Confusers
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are reported when seen. The presence of these
diamond-shaped crystals, which develop from
eosinophil breakdown products, indicates that
an immune response of unknown origin has
taken place. Because such an immune response
may be caused by the presence of parasites, it is
important to examine specimens that contain
Charcot-Leyden crystals closely.
YEAST
The round to oval yeast cells measure 4 to 8 µm
in size and may be confused with protozoan
cysts, especially those of Entamoeba hartmanni
(5 to 12 µm), Entamoeba nana (4 to 12 µm), and
Entamoeba hominis (3 to 10 µm; Fig. 12-8). Furthermore,
there is a considerable resemblance of
a yeast cell to the oocyst of Cryptosporidium (4
to 6 µm). As with the other artifacts and confusers,
yeast cells typically show no definite internal
structures. Occasionally, however, small granules
resembling karyosomes may be seen. Yeast may
be easily distinguished from parasites when seen
in their budding stage.
Quick Quiz! 12-3
What is the clinical significance of the presence of
Charcot-Leyden crystals in a stool or sputum specimen?
(Objective 12-2)
A. Indicative of an immune response of unknown
origin
B. Indicative of a parasitic infection
C. Indicative of a bacterial infection
D. Not a significant finding
PLANT HAIR
Plant hair may resemble helminth larvae in size
and shape (Fig. 12-9). In addition, plant hair may
appear to have a nondescript internal structure.
Upon further examination, plant hair does not
have diagnostic structures, such as a buccal
cavity, esophagus, intestine, or genital primordium.
There is no head or tail region.
Size range: 4-8 m
FIGURE 12-8 Budding yeast.
PLANT MATERIAL
Plant material may range in diameter from 12 to
150 µm and resemble helminth eggs, particularly
an unfertilized Ascaris lumbricoides (38 to
45 µm), in size and shape (Fig. 12-10). This artifact
is typically round to oval in shape and may
or may not have a definite cell wall. Plant material
is often rough in appearance and may have
hairs (pseudocilia) extending from its periphery.
The interior of the cell looks like a cluster of
odd-shaped vacuoles.
FIGURE 12-9 Plant hair.