Tuesday 28 September 2010

Trichomonas vaginalis

(Parasite - Flagellate)

Trichomonas vaginalis is a human parasite which has worldwide distribution and is most commonly isolated from the female genital tract. In the male, Trichomonas vaginalis has been isolated from the prostate so it may be necessary to treat both sexual partners in order to prevent re-infection.

Trichomonas infection in the female may be suspected if a thin frothy white discharge is observed. Diagnosis is best made using a wet preparation from a freshly collected swab. The organism is sensitive to both temperature and drying so it should be sent to the laboratory as quickly as possible without refrigeration. On receipt, a drop of sterile saline is placed on a glass microscope slide and with the swabs contents expelled, it is cover-slipped and examined under low magnification (100-250X).

Trichomonas is roughly pear shaped and is between 7 to 23 µm long by about 5 to 15 µm in size. It normally has 1 posterior and 4 anterior flagella which provides a rather rapid and jerky motility which draws one’s attention when examining fresh preparations. Even in specimens that have been somewhat delayed in transit, an undulating membrane running along a portion of the cell, may be seen beating, An axostyle is also evident running the length of the cell. Other structures may not be evident on an unstained preparation. Trichomonas is only found as a trophozoite as it has no cyst stage.

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Two Trichomonas vaginalis cells (center) seen in a wet prep of a vaginal swab

Trichomonas is site specific and when found in the human genital tract it is diagnostic for Trichomonas vaginalis. Care must be taken not to contaminate the swab with fecal material as the non-pathogenic Trichomonas hominis can be found in stools. Trichomonas tenax may be found as a commensal in the oral cavity.

Gram Stain of Trichomonas in vaginal swab
(note size comparison to wbc's)

Although it is possible for an experienced technologist to see Trichomonas vaginalis in a gram stain, it is not the preparation of choice. A Hematoxylin stain as employed for fecal material examination would stain Trichomonas however the simple wet prep remains both cheaper and quicker. Other tests such as monoclonal antibody, enzyme immunoassay and latex agglutination have been developed. Serological tests have not proven to be effective .
Treatment with Metronidazole (Flagyl) is usually effective although resistant strains have been described.

Short video of motile Trichomonas vaginalis cells in wet prep. Flagellar movement and undulating membrane motion occasionally evident. Will replace with a better video when I get a more active specimen.
(Click on Lower Right Hand of Control Bar to view Full screen)

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