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Staphylococcus epidermidis
📖 About
- Staphylococcus epidermidis is a coagulase-negative staphylococcus (CoNS), part of the normal skin flora, but an opportunistic pathogen in immunocompromised patients or those with indwelling devices.
- Aerobic or facultative anaerobic, making it resilient in varied environments.
🔬 Characteristics
- 🦠 Gram-positive cocci in clusters (“grape-like” appearance).
- 🧪 Catalase positive → differentiates from streptococci.
- ⚪ Non-haemolytic on blood agar (colonies usually white, non-pigmented).
- 🧫 Produces a slime layer (biofilm) → key virulence factor, enabling adhesion to prosthetic material.
- 💊 Novobiocin sensitive → distinguishes from S. saprophyticus (resistant).
🏠 Source
- Normal commensal of the skin flora and mucous membranes.
- Harmless in most healthy individuals but opportunistic in hospital/ITU settings.
⚠️ Pathogenicity
- 🏥 Major cause of nosocomial infections, especially in patients with:
- IV lines, urinary catheters, central venous catheters.
- Prosthetic heart valves, prosthetic joints, vascular grafts.
- ❤️ Infective Endocarditis: Particularly prosthetic valve endocarditis; also in IV drug users (though S. aureus is commoner).
- Biofilm production shields it from immune response and reduces antibiotic penetration.
🛡️ Resistance
- MRSE (Methicillin-resistant S. epidermidis): Mediated by mecA gene encoding altered PBP2a.
- Often resistant to multiple agents (flucloxacillin, erythromycin, aminoglycosides).
- Resistance is commonly plasmid-mediated and transferable.
🔎 Investigations
- 🧪 Coagulase negative → differentiates from S. aureus.
- 💊 Novobiocin sensitive → key distinction from S. saprophyticus.
- ⚪ Colonies: white, non-pigmented, non-haemolytic.
- DNAse negative (unlike S. aureus).
💊 Sensitivity
- Most strains sensitive to Vancomycin (mainstay of treatment for MRSE).
🩺 Management
- 🏥 Infection control: Hand hygiene, aseptic device handling to prevent spread.
- 💊 First-line antibiotic: Vancomycin IV for serious MRSE infections.
- Device-associated infections often require removal/replacement of the prosthesis or catheter in addition to antibiotics.
- Combination therapy (e.g. rifampicin + vancomycin) sometimes used for biofilm infections.
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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