Yes, Staphylococcus lugdunensis is technically a coagulase-negative Staphylococcus, but you must NOT treat it like other coagulase-negative staphylococci—it should be managed as if it were S. aureus 1.
Critical Clinical Distinction
While S. lugdunensis is classified microbiologically as a coagulase-negative Staphylococcus (CoNS) species 2, 3, 4, this classification is dangerously misleading for clinical management. The 2009 IDSA guidelines explicitly state that catheter-related bloodstream infections due to S. lugdunensis should be managed in a manner similar to S. aureus, not like other CoNS 1.
Why This Matters
The virulence profile of S. lugdunensis resembles S. aureus far more than other CoNS species:
Infective endocarditis: S. lugdunensis causes aggressive valve destruction and abscess formation with high mortality rates, similar to S. aureus 4. In comparative studies, 14% of S. lugdunensis bacteremia cases developed endocarditis versus only 2% of S. epidermidis cases 3.
Metastatic infections: 18% of S. lugdunensis bacteremia cases develop metastatic complications, comparable to S. aureus (16%) but dramatically higher than S. epidermidis (5%) 3.
Mortality: Seven-day mortality for S. lugdunensis bacteremia (9%) is significantly higher than S. epidermidis (1%) and similar to S. aureus (7%) 3.
Treatment Approach
When you identify S. lugdunensis, immediately shift your management strategy from the benign approach used for typical CoNS to the aggressive approach used for S. aureus:
- Remove infected catheters promptly 1
- Treat for 4-6 weeks for bloodstream infections (not the 5-7 days used for other CoNS) 1
- Obtain transesophageal echocardiography to evaluate for endocarditis 1
- Search for metastatic foci of infection 3
- Consider infectious disease consultation 2
Antibiotic Susceptibility
Unlike most CoNS, S. lugdunensis remains highly susceptible to most antibiotics 4, 5:
- Penicillin susceptibility: 74.6% in Swedish studies 5, though ranges 15-87% worldwide 5
- Oxacillin resistance: 16% in recent U.S. data 6, though historically rare
- Vancomycin: 100% susceptible 6
- Use S. aureus breakpoints, not CoNS breakpoints, when interpreting susceptibility testing 4
Common Pitfall
The most dangerous error is dismissing S. lugdunensis as "just another CoNS contaminant" when it appears in blood cultures. While other CoNS are frequently contaminants, S. lugdunensis in blood cultures should be presumed pathogenic until proven otherwise, especially with multiple positive culture sets 1, 2.