Gardnerella vaginalis

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Gardnerella
Microscopic picture of vaginal epithelial clue cells coated with Gardnerella vaginalis, magnified 400 times.
Scientific classification
Kingdom: Bacteria
Phylum: Actinobacteria
Class: Actinobacteria
Order: Bifidobacteriales
Family: Bifidobacteriaceae
Genus: Gardnerella
Species: G. vaginalis
Binomial name
Gardnerella vaginalis
(Gardner and Dukes 1955)[1] Greenwood and Pickett 1980[2]

Gardnerella is a genus of Gram-variable-staining facultative anaerobic bacteria of which G. vaginalis is the only species. The organisms are small (1-1.5 µm diameter) non-spore forming, non-motile coccobacilli.

Once classified as Haemophilus vaginalis and afterwards as Corynebacterium vaginalis, Gardnerella vaginalis grows as small, circular, convex, gray colonies on chocolate agar; it also grows on HBT agar. A selective medium for G. vaginalis is colistin-oxolinic acid blood agar.

Clinical significance[edit]

Gardnerella vaginalis is a facultatively anaerobic Gram-variable rod that can cause bacterial vaginosis in some women as a result of a disruption in the normal vaginal microflora. The resident facultative anaerobic Lactobacillus population in the vagina are responsible for the acidic environment. Once the anaerobes have supplanted the normal vaginal bacteria, prescription antibiotics with anaerobic coverage may have to be given to eliminate the G. vaginalis and allow the balance to be restored.

While typically isolated in genital cultures, it may also be detected in other samples from blood, urine, and pharynx. Although G. vaginalis is a major species present in bacterial vaginosis, it can also be isolated from women without any signs or symptoms of infection.

It has a Gram-positive cell wall,[3] but because the cell wall is so thin it can appear either Gram-positive or Gram-negative under the microscope. It is associated microscopically with clue cells, which are epithelial cells covered in bacteria.

G. vaginalis produces a pore-forming toxin, vaginolysin, which affects only human cells.[4]

Protease and sialidase enzyme activities frequently accompany G. vaginalis.[5][6][7][8]

Treatment[edit]

Methods of antibiotic treatment include metronidazole[9] and clindamycin,[10][11] in both oral and vaginal gel/cream forms.

The effectiveness of treating bacterial vaginosis with antibiotics is well-documented.

Symptoms[edit]

Gardnerella vaginalis is the predominant cause of bacterial vaginosis,[12] whose symptoms may be asymptomatic,[13] but can include vaginal discharge, vaginal irritation, and a "fish like" odor. In the "amine whiff test" 10% KOH is added to the discharge, a positive result indicated if a fishy smell is produced. This and other tests can be used to distinguish between vaginal symptoms related to G. vaginalis from those caused by other organisms, such as Trichomonas and Candida albicans, which are similar and may require different treatment. Trichomonas vaginalis and Gardnerella vaginalis have similar clinical presentations and can cause a frothy gray or yellow-green vaginal discharge, pruritus, and produce a positive "whiff-test." The two can be distinguished using a wet mount slide, where a swab of the vaginal epithelium is diluted and then placed onto a slide for observation under a microscope. Gardnerella reveals a classic "clue cell" under the microscope, showing bacteria adhering to the surface of squamous epithelial cells. Both conditions are treated with metronidazole or clindamycin.

Eponym[edit]

It is named after Hermann L. Gardner (1918 – 2005), an American Bacteriologist who discovered it in 1955.

References[edit]

  1. ^ Gardner HL, Dukes CD (1955). "Haemophilus vaginalis vaginitis. A newly defined specific infection previously classified 'Non-specific vaginitis'.". Am J Obstet Gynecol 69: 962–976. 
  2. ^ J. R. Greenwood; M. J. Pickett (January 1980). "Transfer of Haemophilus vaginalis Gardner and Dukes to a New Genus, Gardnerella: G. vaginalis (Gardner and Dukes) comb. nov.". International Journal of Systematic Bacteriology 30 (1): 170–178. doi:10.1099/00207713-30-1-170. 
  3. ^ J Harper and G Davis. Cell Wall Analysis of Gardnerella Vaginalis" Int J Syst Bacteriol 32 (1982), 48-50.
  4. ^ Gelber, S. E.; Aguilar, J. L.; Lewis, K. L. T.; Ratner, A. J. (2008). "Functional and Phylogenetic Characterization of Vaginolysin, the Human-Specific Cytolysin from Gardnerella vaginalis". Journal of Bacteriology 190 (11): 3896–3903. doi:10.1128/JB.01965-07. PMC 2395025. PMID 18390664.  edit
  5. ^ Lopes dos Santos Santiago, G., P. Deschaght, N. El Aila, T. N. Kiama, H. Verstraelen, K. K. Jefferson, M. Temmerman, and M. Vaneechoutte. 2011. Gardnerella vaginalis comprises three distinct genotypes of which only two produce sialidase. Am. J. Obstet. Gynecol. 204:450.e1-450.e7.
  6. ^ Harwich, M. D., Jr., J. M. Alves, G. A. Buck, J. F. Strauss, 3rd, J. L. Patterson, A. T. Oki, P. H. Girerd, and K. K. Jefferson. 2010. Drawing the line between commensal and pathogenic Gardnerella vaginalis through genome analysis and virulence studies. BMC Genomics 11:375.
  7. ^ von Nicolai, H., R. Hammann, S. Salehnia, and F. Zilliken. 1984. A newly discovered sialidase from Gardnerella vaginalis. Zentralbl. Bakteriol. Mikrobiol. Hyg. A. 258:20-26.
  8. ^ Yeoman, C. J., S. Yildirim, S. M. Thomas, A. S. Durkin, M. Torralba, G. Sutton, C. J. Buhay, Y. Ding, S. P. Dugan-Rocha, D. M. Muzny, X. Qin, R. A. Gibbs, S. R. Leigh, R. Stumpf, B. A. White, S. K. Highlander, K. E. Nelson, and B. A. Wilson. 2010. Comparative genomics of Gardnerella vaginalis strains reveals substantial differences in metabolic and virulence potential. PLOS ONE 5:e12411.
  9. ^ Jones BM, Geary I, Alawattegama AB, Kinghorn GR, Duerden BI (August 1985). "In-vitro and in-vivo activity of metronidazole against Gardnerella vaginalis, Bacteroides spp. and Mobiluncus spp. in bacterial vaginosis". J. Antimicrob. Chemother. 16 (2): 189–97. doi:10.1093/jac/16.2.189. PMID 3905748. 
  10. ^ Khan, F. Z. (2011). "Microbial Infections in females of childbearing age and therapeutic interventions". Rawal Medical Journal 36 (3): 178–181. 
  11. ^ Ferris, D.G., Litaker, M.S., Woodward, L., Mathis, D., Hendrich, J. (1995). "Treatment of bacterial vaginosis: a comparison of oral metronidazole, metronidazole vaginal gel, and clindamycin vaginal cream". The Journal of Family Practice 41 (5): 443–449. 
  12. ^ http://www.biomedcentral.com/1471-2180/12/301/abstract
  13. ^ Schwebke, Jane R. (2000). "Asymptomatic bacterial vaginosis". American Journal of Obstetrics & Gynecology 183 (6): 1434–1439. doi:10.1067/mob.2000.107735. 

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