Medical Microbiology

Trichomonasvaginalis

Causativeagentoftrichomonosis

&Trichomonasvaginalisisafrequentflagellatespeciesthatoccursworld-

wideandistransmittedmainlybysexualintercourse.Itcausesvaginitis

inwomenandurethritisinmen. &

Occurrence.Thenumberofnewcasesisestimatedat 170 millionannually

(WHO, 199 8).Inaveragepopulationsofdevelopedcountries,infectionrates

areabout 5 – 20 %inwomenandusuallybelow 5 %inmen.

Parasite,lifecycle,andepidemiology.Trichomonasvaginalisisapear-

shapedprotozoonabout 10 – 20 lmlongand 2 – 14 lmwide(Fig.9. 2 ).Five

flagellaemergefromabasalbodyattheanteriorpole,fourfreelyextendfor-

wardsandoneextendsbackwards,formingtheouteredgeoftheundulating

membrane,whichreachesbackonlyjustbeyondthemiddleofthecell.

Anaxialrodmadeupofmicrotubules(theaxostyle)protrudeswithits

freetipfromtheposteriorendofthecell.Theovalcellnucleusliesnear

theupperpoleoftheprotozoon.Trichomonadsareanaerobicprotozoa

thatpossesshydrogenosomes,whicharespecializedorganellesproducing

H 2 asametabolite.

T.vaginaliscolonizesthemucosaoftheurogenitaltractandreproducesby

longitudinalbinaryfission.Trichomonadsdonotencyst,althoughrounded,

nonmotileformsareobservedwhicharedegeneratedstageswithoutepide-

miologicalsignificance.

Trichomonasvaginalis 481

Trichomonasvaginalis

Anterior flagella

Basal body Nucleus Hydrogenosomes

Trailing flagellum and

undulating membrane

Parabasal body and

Costa Golgi apparatus

Axostyle

Fig.9.2. MorphologyofTrichomonasvaginalis(schematic).

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Kayser, Medical Microbiology © 2005 Thieme