Information About Staphylococcus Epidermidis Gram Stain Test

Submitted on March 27, 2012

Staphylococcus is essentially a type of bacteria that are usually found in the nose and skin of human beings. If viewed under a microscope, they are found to be in microscopic clusters which are like grapes in appearance. There are more than 20 species of staphylococci; however the only two species relevant to us humans are Staphylococcus aureus, and Staphylococcus epidermidis. The stapylococus epidermis is usually found on the skin, while the Staphylococcus aureus is found mainly in the nose, mouth, and gastrointestinal tract of humans. These two are also known to be the cause of boils in human beings.

Staphylococcus Epidermidis Gram Stain Test

A staphylococcus epidermidis gram stain test is a biological procedure wherein microorganisms are stained in order to identify and differentiate between them. Crystal violet, iodine solution, and ethanol are used in this procedure, and those bacteria which retain the stain are referred to as gram positive, while others are referred to as gram negative. Gram negative bacteria may either lose the stain or stain with the counter stain. Staphylococcus aureus retains the purple stain and hence are said to be gram positive. This micro organism also has the ability to ferment glucose in the absence of oxygen, and lactic acid is formed in this process as a result.


Staphylococcus epidermidis gram staining is done by taking a small sample from the culture put on a slide and dried. The slide is then heated to kill the bacteria, flooded with a stain by the name of Gentian violet, left for about 60 seconds, washed off and later treated with grams solution. Afterwards the slide is rinsed with ethanol to decolorize it, gram positive bacteria like the Staphylococcus bacteria will retain the gentian violet-iodine complex and will appear to be blue-black in color.

Staphylococci are perfect spheres in their shape and their size is about 1 micron. The cells of the staphylococci divide in succession in the three mutually perpendicular planes and the sister cells remain attached to each other, thus they grow in clusters that are irregular. Staphylococcus aureus gram stain causes many infections in humans and is usually responsible for boils, styes, and furuncles. Food poisoning, pneumonia, and sometimes infections in the urinary tract are also caused by staphylococcus aureus and thus care should be taken against this.

Staphylococcus epidermidis gram stain usually shows the difference two major types of cell walls. However it is worth noting that not all species of bacteria follow the rule, there are some which may not be stained by grams method.