What is the best antibiotic for an infected kidney stone?

Best Antibiotic for an Infected Kidney Stone

For infected kidney stones, fluoroquinolones (particularly ciprofloxacin) are the first-line antibiotic treatment, provided local resistance rates do not exceed 10%. 1, 2

Understanding Infected Kidney Stones

Infected kidney stones can refer to:

• Stones formed due to urease-producing bacteria (infection stones)
• Secondarily infected stones of any composition
• Stones causing obstruction leading to pyelonephritis 3

Antibiotic Selection Algorithm

First Steps:

1. Obtain urine culture before starting antibiotics 4
2. Establish drainage if obstruction is present (via stent or nephrostomy tube) 1

Empiric Therapy While Awaiting Culture Results:

• First-line option: Fluoroquinolones

  • Ciprofloxacin 500mg twice daily (oral) or 400mg IV 1, 5, 2
  • Extended-release ciprofloxacin 1000mg daily 1
  • Levofloxacin 750mg daily for 5-7 days 1

• If local fluoroquinolone resistance >10%:

  • Initial IV dose of ceftriaxone 1g 1
  • OR aminoglycoside (consolidated 24-hour dose) 1
  • Then transition based on culture results

• For severe infection/sepsis:

  • Carbapenems (particularly ertapenem 1g IV daily) 4

Antibiotic Duration:

• 7-14 days for uncomplicated cases
• Longer courses may be needed for persistent infection 6

Important Considerations

Stone Removal is Essential

• Complete stone removal is the mainstay of treatment for infection stones 3
• Antibiotics alone will not resolve the infection if the stone remains 1, 3

Culture-Directed Therapy

• Adjust antibiotics based on culture results and susceptibility testing 4
• Consider local resistance patterns when selecting empiric therapy 1, 4

Special Situations

• Mixed flora infections: Consider amoxicillin-clavulanate or combination therapy 4, 6
• Enterococcus species: Consider nitrofurantoin or fosfomycin 4
• Resistant organisms: May require specialized antibiotics like ceftazidime-avibactam or meropenem-vaborbactam 4

Pitfalls to Avoid

• Do not treat asymptomatic bacteriuria unless the patient is undergoing urological procedures with mucosal bleeding 4
• Do not use amoxicillin or ampicillin as empiric therapy due to high resistance rates 1
• Do not use fluoroquinolones if local resistance exceeds 10% 1
• Do not continue antibiotics indefinitely without addressing the stone 3, 6

Procedural Considerations

• If purulent urine is encountered during stone removal, abort the procedure, establish drainage, and continue antibiotics 1
• Antimicrobial prophylaxis should be administered prior to stone intervention based on prior urine culture results and local antibiogram 1