Non-pathogenic, cosmopolitan parasite. It does not have a cystic stage: the vegetative form can survive for at least 24 hours in the environment and this enables its transmission.
Pentatrichomonas intestinalis lives in the large intestine (colon, caecum) where it reproduces by binary fission. The active
vegetative form moves in a jerky, progressive, but non-directional
manner. As for other
flagellates, when the trophozoite immobilizes, it
becomes round.
Size: 10-15 μm
long, 7-10 μm wide.
Morphology: tear-dropped shaped. The nucleus, located
at the larger anterior end, contains a small karyosome;
peripheral chromatin is distributed unevenly over the nuclear membrane. Beside
the nucleus is the cytostome, a small groove that is
barely visible.
Flagella: 3-5 long, anteriorly
directed, flagella originate from a group of blepharoplasts
in front of the nucleus. One more flagellum is posteriorly
directed and constitutes, with the body of the parasite, a long, folded, undulating
membrane (plissée).
This flagellum extends way beyond the posterior end of the trophozoite
as a free flagellum. An axostile, a rigid support
structure, runs longitudinally along the entire length of the parasite and extends
from the back with a pointed
end.
Within
the cytoplasm are food vacuoles containing ingested bacteria and yeast. A
typical feature of Pentatrichomonas intestinalis is represented by dark
granules about 1 μm long, called hydrogenosomes: such structures can be seen with trichrome but not with Giemsa’s or
May-Grünwald-Giemsa’s stains (which, besides, do not
always stain flagella and the undulating membrane).