Staphylococcus epidermidis

by Divya Ravinder

Staphylococcus epidermidis
Staphylococcus epidermidis

Shape and Colony Type

Staphylococcus epidermidis is a sphere-shaped bacteria that forms clumps.

Gram Stain Results

S. epidermidis is a gram positive bacteria, which means that the bacteria has a single layer. This was identified when the bacteria absorbed the crystal violet stain which turned it a dark shade of violet. The bacteria's cell wall is composed of peptidoglycan.

Gram Stain of Staphylococcus epidermidis
Gram Stain of Staphylococcus epidermidis

Environment and Metabolism

S. epidermidis grows well on nutrient agar dishes around the temperature of 37°C.

This bacteria produces acidic waste. This was tested using the methyl red test. We put the bacteria in a broth with glucose and we identified its waste based on the color the broth turned. If it was red, there was acidic waste, and if there was yellow, there was basic waste. S. epidermidis clearly produces acidic waste because the broth turned red.

S. epidermidis is a non-motile bacteria, which means that it cannot move. The motility was test by stabbing the agar in a tube and placing some bacteria inside of it and seeing how diffused the bacteria growth was.
S. epidermidis did not perform hemolysis at on the sheep's blood agar plates. Therefore, this bacteria performs "gamma hemolysis".

This strain of bacteria is facultative, which means that it can grow with or without oxygen. This was identified when the bacteria in the nutrient agar plate was put in a glass jar with a lighted candle. The candle used up all the oxygen in the jar so that the bacteria would have to use fermentation to survive.

Antibiotic Sensitivity

Bauer-Kirby tests were conducted on the bacteria streaked on nutrient agar. This bacteria proved to be resistant towards penicillin, chloramphenicol, and amoxycillin. This seems to be due to exposure to antibiotics in sweat, as the bacteria is often found on the skin. Some of the antibiotics that can kill S. epidermidis are vancomycin and rifampin. Vancomycin and rifampin kill the bacteria by inhibiting bacterial cell wall synthesis.


S. epidermidis can cause a biofilm to grow on plastic devices inside the body. It mostly affects mostly medical prosthesis and intravenous catheters. It can also cause endocarditis. It usually occurs on patients with defective heart valves.
Slimy Biofilm of S. Epidermidis on Implanted Medical Device
Slimy Biofilm of S. Epidermidis on Implanted Medical Device