What is the recommended treatment for Staphylococcus lugdunensis infections?

Treatment of Staphylococcus lugdunensis Infections

Staphylococcus lugdunensis infections should be treated with cloxacillin (or other antistaphylococcal penicillins) as first-line therapy since this organism is almost always methicillin-susceptible and responds well to beta-lactam antibiotics. 1

Characteristics of S. lugdunensis

S. lugdunensis is a coagulase-negative staphylococcus (CoNS) with unusual virulence characteristics:

• Unlike other CoNS, it causes aggressive infections similar to S. aureus 1
• High rate of perivalvular extension and metastatic infection in endocarditis cases 1
• Uniformly susceptible to most antibiotics (methicillin resistance is rare) 2
• Approximately 75% of isolates remain susceptible to penicillin G 2

Treatment Algorithm

First-line therapy:

• Antistaphylococcal penicillins (cloxacillin, oxacillin, flucloxacillin) 1
  • Dosage: 12 g/day IV in 4-6 divided doses for serious infections
  • Duration: 4-6 weeks for endocarditis; 5-14 days for skin/soft tissue infections

For penicillin-susceptible strains:

• Penicillin G may be preferred over oxacillin 2
  • MIC values for penicillin G are typically threefold lower than oxacillin in susceptible strains

For penicillin-allergic patients:

• First option: Attempt penicillin desensitization in stable patients 1
• Second option: Daptomycin in combination with another effective antistaphylococcal drug 1
• Third option: Vancomycin (though inferior to beta-lactams) 1
  • Dosage: 15-20 mg/kg every 8-12 hours
  • Target trough levels: 15-20 mg/L

Infection-Specific Considerations

Endocarditis:

• S. lugdunensis endocarditis is highly destructive with mortality rates similar to S. aureus 1
• Early surgical intervention is often necessary due to valve destruction and abscess formation 3, 4
• Antibiotic therapy without cardiac surgery or delayed surgery often follows a fatal course 4

Skin and Soft Tissue Infections:

• Most commonly presents as folliculitis, cutaneous pustulosis, or abscesses 5, 6
• Surgical drainage is essential for purulent collections 7
• Shorter courses (5-14 days) of antibiotics are typically sufficient 5

Important Clinical Considerations

• S. lugdunensis can be underdiagnosed if laboratories do not routinely identify CoNS to the species level 5
• Initial screening can be done with pyrrolidonyl aminopeptidase hydrolysis testing 1
• Patients should be monitored carefully for development of periannular extension or extracardiac spread of infection 1
• Despite being a CoNS, treatment should follow protocols more similar to those for S. aureus due to its virulence 3

Antibiotic Susceptibility

• Methicillin resistance is rare (only about 2-3% of isolates) 2, 3
• Most isolates remain susceptible to a wide range of antibiotics 6
• Breakpoints for S. lugdunensis are higher than those of other CoNS and similar to S. aureus breakpoints 3

For serious infections, especially endocarditis, aggressive treatment with beta-lactams and early surgical intervention when indicated provides the best outcomes for reducing morbidity and mortality associated with this unusually virulent CoNS.