Trichomonas vaginalis
| Trichomonas vaginalis | ||||||||||||||
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| Giemsa-stained culture of T. vaginalis Giemsa-stained culture of T. vaginalis
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| Scientific classification | ||||||||||||||
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| Binomial name | ||||||||||||||
| Trichomonas vaginalis (Donné 1836) |
Overview
Trichomonas vaginalis, an anaerobic, parasitic flagellated protozoan, is the causative agent of trichomoniasis, and is the most common pathogenic protozoan infection of humans in industrialized countries.[1] The WHO has estimated that 180 million infections are acquired annually worldwide. The estimates for North America alone are between 5 and 8 million new infections each year, with an estimated rate of asymptomatic cases as high as 50%.[2]
Protein function
T. vaginalis also has many enzymes that catalyze a number of reactions making the organism relevant to the study of protein function. T. vaginalis lacks mitochondria and other necessary enzymes and cytochromes to conduct oxidative phosphorylation. T. vaginalis obtains nutrients by transport through the cell membrane and by phagocytosis. The organism is able to maintain energy requirements by the use of a small amount of enzymes to provide energy via glycolysis of glucose to glycerol and succinate in the cytoplasm, followed by further conversion of pyruvate and malate to hydrogen and acetate in an organelle called the hydrogenosome.[3]
Morphology
The T. vaginalis trophozoite is oval as well as flagellated. Five flagella arise near the cytosome; four of these immediately extend outside the cell together, while the fifth flagellum wraps backwards along the surface of the organism. The functionality of the fifth flagellum is not known. In addition, a conspicuous barb-like axostyle projects opposite the four-flagella bundle; the axostyle may be used for attachment to surfaces and may also cause the tissue damage noted in trichomoniasis infections.[4]
While T. vaginalis does not have a cyst form, organisms can survive for up to 24 hours in urine, semen, or even water samples. Combined with an ability to persist on fomites with a moist surface for 1 to 2 hours, T. vaginalis is among the most durable protozoan trophozites.
Clinical
Trichomoniasis can occur in females (males rarely exhibit any symptoms of a T. vaginalis infection) if the normal acidity of the vagina is shifted from a healthy, semi-acidic pH (3.8 - 4.2) to a much more basic one (5 - 6) that is conducive to T. vaginalis growth. Some of the symptoms of T. vaginalis include: preterm delivery, low birth weight, and increased mortality as well as predisposing to HIV infection, AIDS, and cervical cancer.[5] T. vaginalis has also been reported in the urinary tract, fallopian tubes, and pelvis and can cause pneumonia, bronchitis, and oral lesions. Other symptoms include inflammation with increasing number of organisms, greenish-yellow frothy vaginal secretions and itching.
T. vaginalis can be detected by studying discharge or with a pap smear and culturing. With a pap smear, infected individuals would have a transparent "halo" around their superficial cell nucleus. T. vaginalis is diagnosed via a wet mount, in which "corkscrew" motility can be observed. Condoms are effective at preventing infection.
Metronidazole or tinidazole can treat an infection in progress, and should be prescribed to sexual partners as well.[6].
Genome Sequencing
Jane Carlton led a project to sequence the Trichomonas vaginalis genome which found that the genome was much larger than was expected.[1] [2]
Treatment
T. vaginalis infection
- Preferred regimen:Metronidazole 2 g PO in a single dose OR Tinidazole 2 g PO in a single dose
- Alternative regimen : Metronidazole 500 mg PO bid for 7 days
T. vaginalis infection in patients with HIV
- Preferred regimen: Metronidazole 500 mg PO bid for 7 days
Persistent or Recurrent Trichomoniasis
- Persistent or Recurrent Trichomoniasis
- Treatment Failure
- Preferred regimen (1):Metronidazole 500 mg PO bid for 7 days
- Treatment failure again
- Preferred regimen (2): Metronidazole 2 g PO for 7 days OR Tinidazole 2 g PO for 7 days
- Preferred regimen (3): Azithromycin 500 mg PO as a single dose, followed by 250 mg PO qd for 4 days
- Preferred regimen (4): Clarithromycin 500 mg PO bid for 10 days
If treatment failure has occurred with metronidazole 2 g single dose and reinfection is excluded, the patient (and their partner[s]) can be treated with metronidazole 500 mg orally twice daily for 7 days. If this regimen fails, clinicians should consider treatment with metronidazole or tinidazole at 2 g orally for 7 days. If several 1-week regimens have failed in a person who is unlikely to have nonadherence or reinfection, testing of the organism for metronidazole and tinidazole susceptibility is recommended (693). CDC has experience with susceptibility testing for nitroimidazole-resistant T. vaginalis and treatment management of infected persons and can provide assistance (telephone: 404–718–4141; website: http://www.cdc.gov/std). Higher dose tinidazole at 2–3g for 14 days, often in combination with intravaginal tinidazole, can be considered in cases of nitroimidazole-resistant infections; however, such cases should be managed in consultation with an expert.
References
- ↑ Soper D (2004). "Trichomoniasis: under control or undercontrolled?". Am J Obstet Gynecol. 190 (1): 281–90. PMID 14749674.
- ↑ Hook E (1999). "Trichomonas vaginalis--no longer a minor STD". Sex Transm Dis. 26 (7): 388–9. PMID 10458631.
- ↑ Upcroft P, Upcroft J (2001). "Drug targets and mechanisms of resistance in the anaerobic protozoa". Clin Microbiol Rev. 14 (1): 150–64. PMID 11148007.
- ↑ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. ISBN 0838585299.
- ↑ Schwebke J, Burgess D (2004). "Trichomoniasis". Clin Microbiol Rev. 17 (4): 794–803, table of contents. PMID 15489349.
- ↑ Cudmore S, Delgaty K, Hayward-McClelland S, Petrin D, Garber G (2004). "Treatment of infections caused by metronidazole-resistant Trichomonas vaginalis". Clin Microbiol Rev. 17 (4): 783–93, table of contents. PMID 15489348.
External links
- TIGR's Trichomonas vaginalis genome sequencing project.
- TrichDB: the Trichomonas vaginalis genome sequencing project
- NIH site on trichomoniasis.
- Taxonomy
cs:Bičenka poševní da:Trichomonas vaginalis de:Trichomonas vaginalis it:Trichomonas nl:Trichomonas vaginalis