Staphylococcus epidermidis

Staphylococcus epidermidis is a member of the bacterial genus Staphylococcus, consisting of Gram-positive cocci arranged in clusters. It is catalase-positive and coagulase-negative and occurs frequently on the skin of humans and animals and in mucous membranes.It is sensitive to the antibiotic Novobiocin; a feature that distinguishes it from the other common coagulase negative organism Staph. saprophyticus. Due to contamination, S. epidermidis is probably the most common species found in laboratory tests.

Although S. epidermidis is usually non-pathogenic, it is an important cause of infection in patients whose immune system is compromised, or who have indwelling catheters. Many strains produce a slime (biofilm) that allows them to adhere to the surfaces of medical prostheses.

S. epidermidis is often resistant to a wide variety of antibiotics, including penicillin and methicillin.

Colonies of S. epidermidis are typically small, white or beige, approximately 1-2 mm in diameter after overnight incubation. The organism is sensitive to desferrioxamine, and this test is used to distinguish it from almost all other staphylococci. Staphylococcus hominis, which is also sensitive, produces acid from trehalose, so it can usually be distinguished from S. epidermidis.

The normal practice of detecting S.epidermidis is by using the Baird Parker agar with egg yolk supplement. Colonies appeared in small, black colonies while confirmation can be done using coagulase test.

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