Trichomonas and Trichomoniasis Flashcards
Morphology: Trichomonas vaginalis
Approximately 5-32 μm long and 2-14 μm wide in size.
4 flagella that project from the organism’s anterior side and 1 flagellum that extends backward across the middle of the organism. This posterior flagellum forms an undulating membrane.
Hydrogenosomes appear as granules along its axostyle and costa.
It has a prominent nucleus
High motility contributes to its pathogenicity
The best way to distinguish the vaginitis form is the
arrangement of hydrogenosomes .
Life cycle: Trichomonas vaginalis
Trichomonas vaginalis resides in the female vagina and Skene’s glands and the male urethra, seminal vesicles.
The parasite exists as trophozoites that divide by
longitudinal fission. They do not form cysts and does not survive well in the external environment.
Trichomonas vaginalis is transmitted among humans, its only known host, primarily by sexual intercourse.
The infection is discouraged by the ordinary acidity of the vagina (PH 4.0-4.5), but the organism cause a shift in the pH towards alkalinity (pH 5 to 6), which encourages its growth.
Metabolism: Trichomonas vaginalis
Aerotolerant anaerobes: Doesn’t use oxygen, but tolerates it.
It degrades carbs incompletely to short chain acids (acetate and lactate) and CO2, regardless of oxygen.
Produces molecular hydrogen in the absence of oxygen which takes place in the hydrogenosomes.
Part of the pyruvate, produced in the cytoplasm is reduced to lactate by lactic dehydrogenase and excreted. This is accompanied by substrate level phosphorylation that produce ATP.
The other part of pyruvate enters Hydrogenosomes where it gets oxidatively decarboxylated by ferredoxins.
In presence of oxygen the electrons accepted by ferredoxins are used to make water molecules.
Under anerobic conditions, the acquired by ferredoxin is transferred by hydrogenase to protons to produce molecular hydrogen.
It has been shown that the ferrouxins reduce the drug metronidazole into toxic substances and that explains the mechanism of action of this important medicine. Resistant strains lacks the enzymes that catalyze this reaction.
Pathogenesis: Trichomonas vaginalis
Infection occurs through sexual intercourse
Most strains have low pathogenicity resulting in high incidence of asymptomatic cases.
In symptomatic cases, the Incubation period is 5 to 28 days.
Inflammation cause itching and copious white discharge (leukorrhea) which is full of trichomonads.
Degeneration of the vaginal epithelium followed by leukocytic infiltration. Vaginal secretions become white or greenish.
In chronic infection there is occasional flare ups.
The organism increase vaginal pH.
May survive in a host for 2+ years
In men the infection is usually asymptotic.
T. vaginalis triggers an immunosuppressive response in monocytes, macrophages, and dendritic cells.
Diagnosis: Trichomonas vaginalis
Diagnosis of trichomoniasis can be confirmed by looking at a sample of vaginal fluid for women or urine for men under a microscope
Growing a culture and PCR are helpful for mild parasitemia
Serological tests, such as rapid antigen tests are also used.
PCR is also used
Epidemiology: Trichomonas vaginalis
Trichomoniasis frequently causes cervical erosion (90%), a factor in malignancy.
The mode of transmission is direct.
It can be found in newborns of an infected mother if not treated.
Risk factors include, age, unsafe sex with multiple partners, and history of other sexually transmitted infections.
Trichomoniasis increases the susceptibility to human immunodeficiency virus (HIV).
Prevention and Control: Trichomonas vaginalis
The disease is controlled by health awareness, abstinence, Safe sex practices, Regular
testing and treatment.
Treatment: Trichomonas vaginalis
The only drug for treatment is metronidazole
Avoid sexual intercourse until the infection is cured, which takes about a week .
Both partners should be treated, to avoid reinfection.
Untreated, trichomoniasis can last for months to years
Suppositories and douches are used to reduce vaginal pH
Symptoms: Trichomonas vaginalis
Symptoms of T. vaginalis infection range from being completely asymptomatic to acute inflammation
Painful intercourse
Pain in abdomen
Vaginal bleeding
Discomfort during urination
Frothy vaginal discharge
Classification: Trichomonas vaginalis
Phylum: Parabasalea (based on their complex mastigont system that includes parabasal fibers)
Class: Trichomonada
Order: Trichomonadida
Family: Trichomonadidae (recognized by anterior tuft of flagella and axostyle)
Genus: Trichomonas
Species: Trichomonas vaginalis
Trichomonadidae
Anterior tuft of flagella Stout median rod called axostyle. Undulating membrane Jerky twisting locomotion Found in intestinal and reproductive tracts. Also found in guts of termites. Do not form cysts. Human: T. tenax and T. vaginalis T. tenax is a harmless commensal in human mouth.
Trichomonas vaginalis
Causes trichomoniasis
Only eukaryote parasite to cause and STD.
Described by scientist Donne and Kunstler.
Hydrogenosomes
Like mitochondrion, but lack DNA and specific proteins in the double membranes.
