Staphylococcus epidermidis is a type of bacteria commonly found on human skin and mucous membranes. It is part of the normal flora, meaning it usually does not cause harm in healthy individuals. However, it can become opportunistic, leading to infections, especially in people with weakened immune systems or those with medical devices like catheters and prosthetic joints. This bacterium is known for its ability to form biofilms, which are protective layers that help it adhere to surfaces and resist treatment. Infections caused by Staphylococcus epidermidis can be challenging to treat due to its resistance to many antibiotics, making it an important concern in healthcare settings.