Coagulase-Negative Staphylococci Species
Coagulase-negative staphylococci (CoNS) comprise all staphylococcal species except Staphylococcus aureus, with the most clinically important species being S. epidermidis, S. haemolyticus, S. lugdunensis, S. hominis, S. saprophyticus, S. capitis, S. warneri, and S. simulans. 1, 2
Primary Species Classification
The CoNS group is defined by the absence of coagulase enzyme production, which distinguishes them from S. aureus (the only coagulase-positive staphylococcus) 1, 2. The major species include:
Most Clinically Relevant Species:
- S. epidermidis - accounts for 63-73% of CoNS infections and is the most common cause of prosthetic valve endocarditis and catheter-related infections 1, 3, 4, 5
- S. haemolyticus - second most significant nosocomial pathogen among CoNS 3, 4, 5
- S. lugdunensis - unique among CoNS for causing virulent infections resembling S. aureus, particularly aggressive endocarditis with high rates of perivalvular extension 1, 2, 6
Other Recognized Species:
- S. hominis 3, 4, 7
- S. saprophyticus - specifically associated with acute urethritis 8, 5
- S. capitis 9, 8, 4
- S. warneri 7, 10
- S. simulans 8, 7
- S. auricularis 8
Clinical Context and Importance
CoNS are primarily healthcare-associated pathogens, causing prosthetic valve endocarditis, catheter-related bloodstream infections, and infections in immunocompromised patients 1, 11, 5. While traditionally considered less virulent than S. aureus, they account for 60-80% of cardiovascular implantable electronic device infections 11.
Critical Species-Specific Considerations:
S. lugdunensis requires special attention - despite being coagulase-negative, it should be managed similarly to S. aureus infections due to its aggressive clinical behavior 2, 6. Many laboratories lack the capability to differentiate S. lugdunensis from other CoNS, which can lead to inadequate treatment 1.
Diagnostic Challenges:
The interpretation of CoNS in blood cultures is problematic because these organisms are both the most common contaminants and the most common cause of catheter-related bloodstream infections 6. Multiple positive blood cultures from different sites with the same species and identical antibiotic susceptibility patterns support true infection rather than contamination 11, 6.
Antibiotic Resistance Patterns
Most CoNS are methicillin-resistant, with resistance rates of 70-74% to multiple antibiotics 9, 4, 5. Vancomycin remains 100% effective, though increasing numbers show reduced glycopeptide susceptibility 4, 5. Rifampin plays a special role in prosthetic device infections by helping eradicate bacteria attached to foreign material 9.