What is the recommended treatment for a urinary tract infection (UTI) caused by Aerococcus urinae?

Treatment of Urinary Tract Infection with Aerococcus urinae

Nitrofurantoin is the recommended first-line treatment for urinary tract infections caused by Aerococcus urinae, demonstrating clinical and microbiological success rates of 71-76%. 1

First-Line Treatment Options

• Nitrofurantoin is the most effective empiric treatment for A. urinae UTIs, with high clinical and microbiological cure rates 1
• Penicillin and amoxicillin are also appropriate treatment options for A. urinae infections, particularly for invasive infections 2, 3
• For uncomplicated cystitis caused by A. urinae, pivmecillinam has demonstrated clinical success 1

Treatment Algorithm

For Uncomplicated A. urinae Cystitis:

• Start with nitrofurantoin (dosing as per standard UTI protocols) 1, 2
• Alternative options include:
  • Fosfomycin 3g single dose 4, 5
  • Pivmecillinam (for A. urinae cystitis specifically) 1
  • Trimethoprim-sulfamethoxazole (if local susceptibility patterns support its use) 4, 5

For Complicated A. urinae UTI or Pyelonephritis:

• Ciprofloxacin has demonstrated success in pyelonephritis cases 1
• Consider parenteral therapy with:
  • Penicillin (first choice for invasive A. urinae infections) 3
  • Ceftriaxone 75 mg/kg every 24h or cefotaxime 150 mg/kg per day divided every 6-8h 4
  • For severe infections, addition of an aminoglycoside to penicillin should be considered 3

Antimicrobial Susceptibility Considerations

• A. urinae demonstrates 100% susceptibility to benzylpenicillin, ampicillin, meropenem, rifampicin, nitrofurantoin, and vancomycin 6
• Approximately 10.9% of A. urinae isolates show resistance to ciprofloxacin 6
• Nitroxoline shows high activity against A. urinae (MIC50/90 1/2 mg/L) and could be considered as an alternative oral treatment option 6
• Treatment duration should generally be no longer than seven days for uncomplicated cases 4

Special Considerations

• A. urinae is often misidentified as streptococci or staphylococci in laboratory testing, potentially leading to underestimation of its prevalence 3
• Older adults with multimorbidity, chronic urinary retention, urologic cancer, or indwelling catheters are at higher risk for A. urinae infections 2
• Invasive A. urinae infections, including bacteremia and endocarditis, are more common in older men with urinary tract abnormalities 3
• Obtain urine culture before initiating treatment to confirm the diagnosis and guide antimicrobial therapy 4

Common Pitfalls to Avoid

• Failing to obtain pre-treatment urine cultures in patients with suspected A. urinae UTI 4
• Using fluoroquinolones as first-line therapy due to increasing resistance rates (approximately 10.9%) 6
• Treating asymptomatic bacteriuria, which can foster antimicrobial resistance and increase recurrence episodes 4
• Inadequate treatment duration, which should generally be 7 days for uncomplicated cases 4