What is the Difference Between Trichomonas and Gardnerella

The main difference between Trichomonas and Gardnerella is that Trichomonas is a flagellated protozoan, whereas Gardnerella is a facultative anaerobic bacterium.

Trichomonas and Gardnerella are two pathogens that cause infections in the reproductive system of humans. Trichomonas causes trichomoniasis, while Gardnerella causes bacterial vaginosis.

Key Areas Covered

1. What is Trichomonas
     – Definition, Features, Importance
2. What is Gardnerella
     – Definition, Features, Importance
3. Similarities Between Trichomonas and Gardnerella
     – Outline of Common Features
4. Difference Between Trichomonas and Gardnerella
     – Comparison of Key Differences

Key Terms 

Gardnerella, Trichomonas

Difference Between Trichomonas and Gardnerella - Comparison Summary

What is Trichomonas

Trichomonas vaginalis is the pathogen that causes trichomoniasis, one of the most prevalent sexually-transmitted infections that is non-viral. The symptoms of the disease in women include vaginal discharge, pelvic pain, painful intercourse, vaginal itching, and urinary tract infection symptoms. However, males are usually asymptomatic and possible symptoms in men include penile discharge, dysuria, testicular pain, cloudy urine, or urinary frequency. Trichomonas is a motile organism that lives in the prostate and urethra in men and the lower genitourinary tract of women.

Compare Trichomonas vs Gardnerella

Figure 1: Trichomonas

Furthermore, it is a motile protozoan with a size comparable to a white blood cell. It also contains at least four flagella. It usually resides in the urogenital tract. However, it secretes cytotoxic proteins into the epithelial lining, destroying it. Additionally, vaginal pH increases during the infection. The incubation period of Trichomonas is 5-28 days. 

What is Gardnerella

Gardnerella vaginalis is a facultative anaerobic bacterium that causes bacterial vaginosis (BV). However, this bacterium is a part of the normal vaginal flora, and overgrowth causes BV. It forms a biofilm during the progression to BV. It is also the most common cause of vaginal discharge. Furthermore, it is thought that this bacterium is sexually transmitted between partners, and therefore, it increases the risk of HIV infection and the risk of other sexually-transmitting diseases. However, it is not considered contagious.

Trichomonas vs Gardnerella

Figure 2: Normal and BV Flora

The presence of clue cells is a characteristic feature of bacterial vaginosis. They are the epithelial cells of the vagina covered by rod-shaped bacteria. Another distinguishing feature of Gardnerella is the production of vaginosis, a pore-forming toxin that can affect human cells. It induces the target cell lysis allowing the Gardnerella’s virulence. In addition, the bacterium produces proteases and sialidase enzymes necessary as virulence factors. 

Similarities Between Trichomonas and Gardnerella

  • Trichomonas and Gardnerella are two pathogens that cause vaginitis.
  • Both cause vaginal discharge.
  • They produce vaginal pH >4.5.
  • They are anaerobic microorganisms.
  • Metronidazole is prescribed for the treatment of both diseases.
  • They increase the risk of HIV infection. 

Difference Between Trichomonas and Gardnerella


Trichomonas refers to single-celled protozoan parasites best known in medicine because one species causes vaginitis. In contrast, Gardnerella refers to an anaerobic bacterium that is the causative agent in bacterial vaginosis (BV).

Type of Pathogen

Trichomonas is a flagellated protozoan, while Gardnerella is a facultative anaerobic bacterium.

Type of Disease

Moreover, Trichomonas causes trichomoniasis, while Gardnerella causes bacterial vaginosis.


Trichomonas resides in the urogenital tract, while Gardnerella occurs in the vaginal flora. 

Type of Discharge

Trichomonas produces yellow-green, frothy, adhesive, and increasing discharge, while Gardnerella produces thin, homogenous, white-gray, often-increased discharge.


While Trichomonas does not produce inflammation, Gardnerella produces inflammation. 

Laboratory Examination

Motile trichomonads can be observed under the microscope in Trichomonas infections, while clue cells can be observed under the microscope in Gardnerella

Whiff Test

Trichomonas produces a positive whiff test, while Gardnerella produces a negative whiff test. 


In brief, Trichomonas and Gardnerella are pathogens causing vaginitis. Trichomonas is a flagellated protozoan that causes trichomoniasis. It produces yellow-green, frothy, and adherent discharge. It does not produce inflammation. Motile trichomonads can be observed under the microscope. It has positive results for the whiff test. In comparison, Gardnerella is an anaerobic bacterium that causes bacterial vaginosis. It produces a thin, homogenous, white-gray color discharge with inflammation. Clue cells can be observed under a microscope in bacterial vaginosis. Therefore, the main difference between Trichomonas and Gardnerella is the type of disease they cause. 

  1. Schumann JA, Plasner S. Trichomoniasis. [Updated 2022 Jun 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.
  2. Kairys N, Garg M. Gardnerella. [Updated 2022 Aug 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.
Image Courtesy:
  1. Trichomonas vaginalis (20)” By fickleandfreckled – Own work (CC-BY 2.0) via Commons Wikimedia
  2. Normal and BV flora” By Dr Graham Beards – Own Work (CC-BY SA 4.0) via Commons Wikimedia

About the Author: Lakna

Lakna, a graduate in Molecular Biology and Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things. She has a keen interest in writing articles regarding science.

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