Staphylococcus lugdunensis: High-Virulence CoNS and qPCR Detection

1. Key Identification Features
S. lugdunensis is typically coagulase-negative, although 1–5% of strains may produce weak or variant coagulase, leading to potential misidentification.

2. High Virulence Profile
Unlike other coagulase-negative staphylococci, it produces multiple virulence factors:

• Adhesins enabling strong tissue colonization
• Biofilm formation enhancing resistance to host immunity and antibiotics
• Hemolysins causing host cell and tissue damage
• Proteases and lipases facilitating tissue invasion and spread

This organism grows readily on standard media such as blood agar, chocolate agar, and tryptic soy agar.

Optimal growth occurs at 35–37°C under aerobic or facultative anaerobic conditions, with visible colonies appearing within 24–48 hours.

Colony Features (Blood Agar):

• 24 h: small colonies (1–2 mm), smooth, round, convex
• 48 h: enlarged (3–5 mm), sometimes irregular with central depression
• Color: gray-white or cream
• β-hemolysis: present in >95% of strains (key distinguishing feature)
• Adhesiveness: strong “stringing” when touched with a loop

1. Infective Endocarditis
Highly aggressive, often affecting native valves and leading to valve destruction, abscess formation, embolism, and heart failure.

2. Bone and Joint Infections
Includes osteomyelitis, septic arthritis, and discitis, often causing significant tissue destruction.

3. Skin and Soft Tissue Infections
Can result in abscesses, cellulitis, surgical site infections, and even necrotizing fasciitis.

4. Bacteremia and Sepsis
May arise as primary or secondary infection with potential metastatic spread.

5. Other Infections
Includes urinary tract infections, peritonitis, endophthalmitis, and CNS infections.

1. Initial Screening

• Gram-positive cocci in clusters
• Coagulase-negative (with possible weak positives)
• Strong β-hemolysis and colony adhesiveness

2. Biochemical Tests

• Pyrrolidonyl arylamidase (PYR): positive
• Ornithine decarboxylase: positive
• β-glucosidase: negative
• Novobiocin: sensitive

3. Advanced Methods

• MALDI-TOF MS: rapid and accurate identification
• 16S rRNA sequencing: gold standard for confirmation

1. Resistance Profile

• Low methicillin resistance (most strains lack mecA gene)
• Some strains produce β-lactamase (penicillin resistance)
• Variable resistance to macrolides, aminoglycosides, and fluoroquinolones

2. Treatment Strategies

First-line:
Anti-staphylococcal penicillins (e.g., oxacillin, flucloxacillin)

Alternatives:

• β-lactam/β-lactamase inhibitor combinations
• Cephalosporins (e.g., cefazolin)
• Glycopeptides (vancomycin, teicoplanin) for severe cases
• Daptomycin, linezolid, or TMP-SMX based on susceptibility

Combination therapy (e.g., rifampin) is recommended for biofilm-associated or prosthetic infections.