What are the recommended antibiotics for a Staphylococcus lugdunensis urinary tract infection (UTI)?

Treatment of Staphylococcus lugdunensis UTI

For Staphylococcus lugdunensis urinary tract infections, penicillin G is the optimal first-line antibiotic choice when the isolate is penicillin-susceptible, as it demonstrates superior in vitro activity compared to oxacillin, with MIC values threefold lower. 1

Primary Treatment Approach

First-Line Therapy

• Penicillin G should be prioritized for penicillin-susceptible S. lugdunensis UTI, as approximately 75% of isolates remain susceptible to penicillin, and penicillin G achieves significantly lower MIC50 and MIC90 values than oxacillin 1
• This represents a critical distinction from other staphylococcal infections, where anti-staphylococcal penicillins are typically preferred 1

Alternative First-Line Options

If penicillin resistance is documented or suspected:

• Trimethoprim-sulfamethoxazole (TMP-SMX) - the majority of S. lugdunensis isolates demonstrate susceptibility 1
• Fluoroquinolones (ciprofloxacin, levofloxacin) - high susceptibility rates maintained 1
• Clindamycin - excellent activity against most isolates 1

Classification and Management Strategy

Determine UTI Complexity

S. lugdunensis UTI should be classified as:

• Uncomplicated lower UTI (cystitis in otherwise healthy women): Treat with oral agents for 5-7 days 2
• Complicated UTI (males, anatomic abnormalities, catheter-associated, immunosuppression): Requires broader consideration and potentially longer duration 2, 3

For Uncomplicated S. lugdunensis Cystitis

• Oral penicillin G (if susceptible) or TMP-SMX for 5-7 days 1, 2
• Nitrofurantoin is an acceptable alternative given the general susceptibility profile of S. lugdunensis, though specific data is limited 2
• Fosfomycin single 3-gram dose may be considered, though breakpoints for staphylococci are not well-defined 1, 4

For Complicated S. lugdunensis UTI

• Obtain urine culture and susceptibility testing before initiating therapy 2, 3
• If empiric therapy is needed, use TMP-SMX or a fluoroquinolone pending culture results 2, 3
• Once susceptibilities are available, narrow to the most appropriate agent, preferably penicillin G if susceptible 1
• Duration: 7-14 days depending on clinical response and complicating factors 2, 3

Critical Considerations

Methicillin Resistance

• Methicillin resistance is rare in S. lugdunensis (mecA gene carriage uncommon), but when present, requires alternative therapy 1
• If methicillin-resistant S. lugdunensis (MRSL) is identified, treatment options include:
  • Vancomycin for severe infections 2
  • Linezolid for oral therapy 2
  • TMP-SMX or doxycycline if susceptible 2, 1

Antibiotic Stewardship

• Avoid fluoroquinolones as first-line for uncomplicated UTI due to collateral damage concerns and FDA warnings about adverse effects 2
• Reserve fluoroquinolones for complicated cases or when other options are unsuitable 2
• Beta-lactams other than penicillin G (such as cephalosporins) are not optimal first-line choices due to inferior activity and propensity to promote recurrence 2

Common Pitfalls

• Do not assume S. lugdunensis behaves like other coagulase-negative staphylococci - it maintains unusual susceptibility to penicillin unlike most CoNS 1
• Do not automatically use vancomycin - this organism typically remains susceptible to multiple oral agents, making vancomycin unnecessary for most UTI cases 1
• Always obtain susceptibility testing for staphylococcal UTIs, as resistance patterns can vary geographically (penicillin resistance ranges 15-87% worldwide) 1