What does Gardnerella look like?

Gardnerella (specifically Gardnerella vaginalis) is a small, nonmotile bacterium that appears as a coccobacillus under the microscope and forms distinct colonies when grown on laboratory media.

Microscopic Appearance of Gardnerella

Under a microscope, Gardnerella vaginalis has specific characteristics that distinguish it:

• Size: These organisms are quite small, typically measuring between 1.0 and 1.5 micrometers (μm) in diameter.
• Shape: They are classified as coccobacilli, which means they have a shape that is intermediate between a sphere (coccus) and a rod (bacillus). They are short, oval-shaped rods.
• Motility: Gardnerella is nonmotile, meaning it does not possess flagella or other structures that allow it to move independently.
• Spore Formation: It is a non-spore-forming bacterium, which means it does not produce resistant spores to survive harsh conditions.

Macroscopic Appearance (Colony Morphology)

When grown in a laboratory setting on specific culture media, Gardnerella vaginalis forms characteristic colonies that can be observed with the naked eye:

• On Chocolate Agar: On chocolate agar, colonies of Gardnerella vaginalis are typically:
  • Small: They do not grow into large, sprawling colonies.
  • Circular: The edges of the colonies are generally smooth and round.
  • Convex: They have a slightly raised, dome-like appearance.
  • Gray: Their color is typically a dull gray.
• On HBT Agar: Gardnerella vaginalis is also known to grow well on Human Blood Bilayer Tween (HBT) agar, another specialized medium.

Summary of Characteristics

Here's a quick overview of what Gardnerella looks like:

Understanding these visual characteristics is crucial for laboratory identification of Gardnerella vaginalis, particularly in clinical diagnostics related to conditions like bacterial vaginosis.