What is the recommended treatment for Staphylococcus lugdunensis infections?

Treatment of Staphylococcus lugdunensis Infections

Staphylococcus lugdunensis should be treated like Staphylococcus aureus rather than other coagulase-negative staphylococci, using oxacillin or nafcillin as first-line therapy for susceptible strains, with treatment duration and surgical approach determined by the specific infection type. 1

Key Clinical Recognition

S. lugdunensis is an unusually virulent coagulase-negative staphylococcus that behaves clinically like S. aureus, causing aggressive infections with high rates of complications including valve destruction, perivalvular extension, and metastatic spread. 1 This organism requires species-level identification through specialized biochemical assays or matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry, as standard coagulase-negative staphylococcus identification is insufficient. 1, 2

Antibiotic Selection by Infection Type

Infective Endocarditis (Native Valve)

• First-line for oxacillin-susceptible strains: Oxacillin or (flu)cloxacillin 12 g/day IV in 4-6 divided doses for 4-6 weeks 1
• Add gentamicin 3 mg/kg/day IV in 2-3 doses for the first 3-5 days (though clinical benefit not formally demonstrated and associated with increased toxicity) 1
• For penicillin allergy or methicillin resistance: Vancomycin 30 mg/kg/day IV in 2 doses for 4-6 weeks, with trough levels of 10-15 mg/L 1

Prosthetic Valve Endocarditis

• Oxacillin-susceptible strains: Oxacillin 12 g/day IV in 4-6 doses PLUS rifampin 1200 mg/day IV or orally in 2 doses PLUS gentamicin 3 mg/kg/day IV in 2-3 doses, all for 6 weeks minimum 1
• Methicillin-resistant strains: Vancomycin 30 mg/kg/day IV in 2 doses PLUS rifampin 1200 mg/day PLUS gentamicin 3 mg/kg/day, all for 6 weeks, with vancomycin trough levels of 25-30 mg/L 1
• Rifampin is critical for prosthetic device infections as it eradicates bacteria attached to foreign material, but must always be combined with another effective antistaphylococcal agent to prevent resistance. 1

Prosthetic Joint Infections

• Two-stage revision is strongly recommended as it achieves 85% cure rate compared to 33% for other treatment modalities (P=0.009) 3
• Debridement alone results in 44% relapse rate, while no surgical intervention or one-stage revision results in 100% relapse regardless of antibiotic regimen 3
• Antibiotic therapy: Oxacillin-based regimen for susceptible strains (all isolates except one were oxacillin-susceptible in the largest series) 3
• Prolonged antibiotic course is required in conjunction with aggressive surgical management 3

Skin and Soft Tissue Infections

• For oxacillin-susceptible strains (which represent the vast majority): Oxacillin, dicloxacillin, or cephalexin for 5-21 days depending on severity 4, 5
• Penicillin G may be superior to oxacillin when susceptible, as MIC50 and MIC90 values for penicillin G are threefold lower than oxacillin among penicillin-susceptible isolates 6
• Most infections resolve with appropriate oral antibiotics, with or without surgical drainage 4, 5
• Common presentations include folliculitis/pustulosis (55%), abscesses, surgical wound infections, and secondary infection of hidradenitis suppurativa 4, 5

Antimicrobial Susceptibility Profile

• Penicillin resistance varies widely (15-87% worldwide), but methicillin resistance remains rare 6, 2
• S. lugdunensis remains highly susceptible to most antibiotics, which is uncharacteristic of other coagulase-negative staphylococci 6, 2
• Breakpoints for S. lugdunensis are higher than other coagulase-negative staphylococci and similar to S. aureus breakpoints 2
• Among 540 Swedish isolates, 74.6% were susceptible to penicillin G, with only 2 isolates carrying mecA gene (SCCmec type IVa) 6

Critical Clinical Pitfalls

Do not treat S. lugdunensis like other coagulase-negative staphylococci. The European Society of Cardiology explicitly excludes S. lugdunensis from standard coagulase-negative staphylococcus treatment protocols due to its aggressive behavior. 1 This organism causes IE with a protracted course associated with higher rates of complications and treatment failure (up to 40%). 1

Early surgical intervention is often necessary due to high rates of perivalvular extension, valve destruction, and metastatic infection. 1 The ESC guidelines list S. lugdunensis as a microorganism with "high potential for rapid destruction of cardiac structures" warranting consideration of early surgery. 1

Monitor closely for complications including abscess formation, pseudoaneurysms, fistulas, conduction disturbances, and extracardiac spread, as these occur more frequently than with other coagulase-negative staphylococci. 1

Monitoring Parameters

• Gentamicin levels (when used): Pre-dose (trough) <1 mg/L, post-dose (peak at 1 hour) 10-12 mg/L, with renal function and levels monitored weekly 1
• Vancomycin levels: Trough 10-15 mg/L for native valve IE, 25-30 mg/L for prosthetic valve IE 1
• Clinical response: Continue therapy at least 48 hours after patient becomes afebrile, asymptomatic, and cultures are negative 7, 8