What is the recommended treatment for an elderly man with one kidney and a urine culture showing Staphylococcus (Staph) coagulase-positive?

Treatment for Staphylococcus Coagulase-Positive UTI in Elderly Man with One Kidney

For an elderly man with one kidney and a urine culture showing Staphylococcus coagulase-positive (S. aureus), appropriate antimicrobial therapy should include a penicillinase-resistant penicillin such as flucloxacillin or dicloxacillin if methicillin-susceptible, or vancomycin if methicillin-resistant, with treatment duration of 10-14 days.

Diagnostic Considerations

Before initiating treatment, it's important to distinguish between true infection and asymptomatic bacteriuria:

• Staphylococcus aureus in urine is rarely a contaminant and usually represents true infection
• Significant bacteriuria is defined as ≥50,000 CFUs/mL of a single uropathogen 1
• Assess for symptoms such as:
  • Dysuria
  • Frequency
  • Urgency
  • Suprapubic discomfort
  • Fever
  • Flank pain (particularly important with single kidney)

Treatment Algorithm

Step 1: Determine Methicillin Susceptibility

• Obtain susceptibility testing results before finalizing treatment

Step 2: Select Appropriate Antimicrobial

For Methicillin-Susceptible S. aureus (MSSA):

• First-line: Penicillinase-resistant penicillins (flucloxacillin, dicloxacillin) 2
• Alternatives (for penicillin allergy):
  • First-generation cephalosporins (cefazolin IV or cephalexin oral) - avoid in immediate penicillin hypersensitivity
  • Clindamycin (if susceptible)

For Methicillin-Resistant S. aureus (MRSA):

• First-line: Vancomycin IV 2
• Alternatives (for vancomycin allergy or intolerance):
  • Teicoplanin
  • Linezolid
  • Daptomycin (though less effective for UTI due to poor urinary concentration)

Step 3: Determine Treatment Duration

• 10-14 days for complicated UTI 3
• Consider this case complicated due to:
  • Elderly patient
  • Single kidney
  • S. aureus as the causative organism

Step 4: Renal Dose Adjustment

• Adjust antibiotic dosing based on estimated GFR
• For vancomycin, monitor drug levels and renal function closely
• Calculate GFR before prescribing using online calculators 1

Special Considerations for Elderly Patient with One Kidney

1. Renal Function Monitoring:

   • Baseline renal function assessment before starting therapy
   • Regular monitoring during treatment
   • Avoid nephrotoxic agents if possible

2. Antimicrobial Stewardship:

   • Avoid fluoroquinolones if possible due to adverse effects in elderly 3
   • Consider aminoglycosides only if no alternatives available due to nephrotoxicity risk 1

3. Source Control:

   • Evaluate for potential sources of S. aureus bacteremia
   • Consider echocardiography if bacteremia is present to rule out endocarditis
   • Remove any indwelling urinary catheters if present 3

4. Follow-up:

   • Repeat urine culture after completion of therapy to ensure clearance
   • Monitor for recurrence or complications

Pitfalls and Caveats

1. Avoid treating asymptomatic bacteriuria in the elderly unless preparing for urologic procedures 3

2. Distinguish between delirium and UTI in elderly patients:

   • Mental status changes alone should not trigger antibiotic treatment for bacteriuria 3
   • Look for specific urinary symptoms or signs of systemic infection

3. Consider S. aureus bacteremia:

   • S. aureus in urine may represent hematogenous spread
   • Obtain blood cultures before starting antibiotics
   • If bacteremia is present, extend treatment to 4-6 weeks 3

4. Avoid empiric fluoroquinolones due to:

   • High resistance rates
   • Risk of adverse effects in elderly
   • Potential for C. difficile infection

By following this approach, you can effectively manage Staphylococcus coagulase-positive UTI in an elderly patient with one kidney while minimizing risks of treatment failure and adverse effects.