[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 4 The Flagellates
Four anterior flagella
Nucleus
Costa
Undulating membrane
(half of body length)
One posterior flagellum
Posterior axostyle
Axostyle
Granules along
axostyle common
A
Size range: up to 30 m long
B
Average length: 8-15 m
FIGURE 4-15 A, Trichomonas vaginalis trophozoite. B, Phase contrast wet mount micrograph of a vaginal discharge
revealing the presence of Trichomonas vaginalis protozoa surrounding a squamous epithelial cell. (B from Mahon CR,
Lehman DC, Manuselis G: Textbook of diagnostic microbiology, ed 4, St Louis, 2011, Saunders; courtesy Centers for
Disease Control and Prevention, Atlanta.)
TABLE 4-12
Parameter
Size range
Shape
Motility
Nuclei
Flagella
Other features
Trichomonas vaginalis
Trophozoite: Typical
Characteristics at a Glance
Description
Up to 30 µm long
Ovoid, round or pear-shaped
Rapid, jerky
One, ovoid, nondescript
All originating anteriorly:
Three to five extending
anteriorly
One extending posteriorly
Undulating membrane extending
half of body length
Prominent axostyle that often
curves around nucleus;
granules may be seen along
axostyle
Cyst. There is no known T. vaginalis cyst
stage.
Laboratory Diagnosis
T. vaginalis trophozoites may be recovered using
standard processing methods (see Chapter 2) in
spun urine, vaginal discharges, urethral discharges,
and prostatic secretions. Although permanent
stains may be performed, examination of
saline wet preparations is preferred in many
cases. Not only does the prompt examination of
saline wet preparations allow the practitioner to
observe the organism’s active motility readily,
as well as the other typical characteristics, the
testing may be performed in a relatively short
amount of time. Additional diagnostic tests
available include phase contrast microscopy,
Papanicolaou (Pap) smears, fluorescent stains,
monoclonal antibody assays, enzyme immunoassays,
and cultures.
A DNA-based assay has been developed for T.
vaginalis detection using Affirm VPIII (BD Diagnostics,
Sparks, MD). The sensitivity and specificity
of this method of testing is much greater
than with standard processing methods.
Another diagnostic tool used by laboratories
today is InPouch TV (BioMed Diagnostics, White
City, OR) culture system. This method can be
used with vaginal swabs from women, urethral
swabs from men, urine sediment and semen
sediment. This method requires incubation
time and takes up to 3 days before a result is
determined.