- Staphylococcus epidermidis is a species of Gram-positive cocci that belongs to the Staphylococcus genus. It is a part of the normal flora of human skin and mucous membranes, especially found on the epidermis, hence the name. Unlike its more pathogenic relative Staphylococcus aureus, S. epidermidis is generally not harmful in healthy individuals but can become opportunistic and cause infections in certain situations.
- S. epidermidis is coagulase-negative, which helps distinguish it from S. aureus, and it is also catalase-positive, like all Staphylococcus species. In laboratory tests, it forms small, white, non-hemolytic colonies on blood agar. It is non-motile, non-spore-forming, and grows well in aerobic and anaerobic conditions.
- Although usually harmless, S. epidermidis is a major cause of hospital-acquired (nosocomial) infections, particularly in patients with indwelling medical devices such as catheters, prosthetic joints, pacemakers, and heart valves. This is because the bacterium is capable of forming biofilms, which are protective layers that allow it to stick to surfaces and resist antibiotics and immune system attacks. Once inside the body, especially in immune-compromised individuals, it can cause bacteremia, endocarditis, urinary tract infections, and infections of implanted devices.
- Antibiotic resistance is a significant issue with S. epidermidis. Many strains are resistant to commonly used antibiotics, including methicillin, making treatment challenging. Infections caused by methicillin-resistant S. epidermidis (MRSE) often require treatment with stronger antibiotics such as vancomycin.
- In summary, while Staphylococcus epidermidis is usually a harmless resident of the skin, it becomes clinically important in hospital settings and in people with weakened immune systems or implanted medical devices. Its ability to form biofilms and resist antibiotics makes it a significant concern in modern medicine.
