From the Guidelines
Staphylococcus epidermidis is a gram-positive bacterium that naturally colonizes human skin and mucous membranes as part of the normal microbiota. It is the most common coagulase-negative staphylococcal species found on human skin, particularly in moist areas like the axillae, nares, and groin. While S. epidermidis is generally considered commensal and non-pathogenic in healthy individuals, it can become an opportunistic pathogen, especially in immunocompromised patients or those with implanted medical devices. According to a study published in 2017 1, S. epidermidis has been found to secrete antimicrobial activities that inhibit S aureus growth and biofilm formation, and it can also stimulate Toll-like receptor 2 to induce production of keratinocyte-derived antimicrobial peptides and increased tight junctions to enhance the skin barrier. It is a leading cause of nosocomial infections associated with catheters, prosthetic joints, heart valves, and other medical implants due to its ability to form biofilms on these surfaces. These biofilms protect the bacteria from antibiotics and host immune responses, making infections difficult to treat. S. epidermidis infections typically require treatment with antibiotics such as vancomycin, linezolid, or daptomycin, particularly when dealing with methicillin-resistant strains, as noted in a study from 1995 1. The bacterium's ubiquitous presence on skin makes it a common contaminant in blood cultures, requiring careful clinical interpretation to distinguish between true infection and contamination.
Some key points to consider about S. epidermidis include:
- Its ability to form biofilms on medical devices, which can lead to difficult-to-treat infections
- Its role in inhibiting S aureus growth and biofilm formation through antimicrobial activities
- Its potential to stimulate Toll-like receptor 2 and enhance the skin barrier
- The need for careful clinical interpretation of blood cultures due to its common presence on skin
- The importance of considering methicillin resistance when treating S. epidermidis infections.
From the Research
Characteristics of Staph Epidermis
- Staphylococcus epidermidis is a permanent member of the normal human microbiota, commonly found on skin and mucous membranes 2
- It is capable of establishing a lifelong commensal relationship with humans, providing benefits such as out-competing more virulent pathogens 2
- S. epidermidis can form biofilm on implanted foreign bodies, making it an important opportunistic pathogen in patients receiving medical devices 2, 3
Role in Infections
- S. epidermidis is the most common cause of implant-associated infections and is a canonical opportunistic biofilm former 4
- It can contribute to the pathogenesis of common skin diseases, and its interactions with the host exist on a spectrum of potential pathogenicity derived from its high strain-level heterogeneity 4
- S. epidermidis causes approximately 20% of all orthopedic device-related infections (ODRIs), increasing up to 50% in late-developing infections 2
Antibiotic Resistance and Treatment
- S. epidermidis has developed significant resistance to several antibiotics, making treatment challenging 3, 5
- Newer antimicrobial agents such as daptomycin, linezolid, and ceftaroline have shown effectiveness against S. epidermidis biofilms and resistant strains 3, 5, 6
- The susceptibility profile of S. epidermidis to various antibiotics, including vancomycin, tigecycline, linezolid, daptomycin, and quinupristin/dalfopristin, has been evaluated in several studies 6