Staphylococcus epidermidis Rarely Causes Folliculitis in Healthy Adults
No, Staphylococcus epidermidis does not commonly cause folliculitis in healthy adults—this condition is typically caused by Staphylococcus aureus, not S. epidermidis. 1
The Causative Organism
The IDSA guidelines explicitly state that furuncles and folliculitis are "usually caused by S. aureus" 1. This distinction is critical because:
S. aureus is the pathogenic culprit: Folliculitis involves inflammation where pus is limited to the epidermis, and when it extends deeper into the dermis and subcutaneous tissue, it becomes a furuncle (boil). Both are S. aureus infections 1.
S. epidermidis is a commensal, not a pathogen in this context: S. epidermidis is the most common skin commensal organism and is primarily associated with biofilm formation on indwelling medical devices and prosthetic infections 2, 3. It is not a typical cause of primary skin infections like folliculitis in immunocompetent hosts.
Supporting Evidence
A histological study examining 39 cases of folliculitis found that when bacteria were identified in inflamed follicles, Staphylococcus species (predominantly S. aureus) were present in only 18% of cases 4. Importantly, when S. epidermidis was isolated in one case report of eosinophilic pustular folliculitis, it was considered an incidental finding rather than the causative agent 5.
The skin's innate immune system can differentiate between these two organisms: healthy human skin tissue resident cells, particularly Langerhans cells, produce a discriminatory IL-1β response to S. aureus but not to S. epidermidis, suggesting the immune system recognizes S. aureus as a potential pathogen while tolerating S. epidermidis as a commensal 6.
Clinical Implications
When evaluating folliculitis in a healthy adult:
- Assume S. aureus as the pathogen, particularly in the current era where community-acquired MRSA is prevalent
- Culture is recommended for carbuncles and abscesses but reasonable to treat empirically for typical folliculitis 1
- S. epidermidis isolated from superficial skin cultures is almost always a contaminant or colonizer, not the disease-causing organism
- Reserve concern for S. epidermidis infections to patients with prosthetic devices, central lines, or other foreign bodies 2
Common Pitfall
Do not attribute folliculitis to S. epidermidis simply because it grows in culture—this organism colonizes 100% of human skin and will grow from virtually any skin swab. Its presence does not equal causation in immunocompetent patients with folliculitis 3.