Aerococcus urinae Antibiotic Treatment
For Aerococcus urinae infections, penicillin or amoxicillin should be the first-line treatment, with combination therapy using an aminoglycoside (gentamicin) reserved for severe invasive infections such as endocarditis or bacteremia. 1, 2
First-Line Treatment for Uncomplicated UTI
- Amoxicillin 500 mg orally every 8 hours for 7 days is the preferred regimen for uncomplicated urinary tract infections caused by A. urinae, as this organism demonstrates consistently low MICs to penicillins 1
- Penicillin is equally effective and represents an appropriate alternative for less severe cases 1, 2
- Nitrofurantoin is also an effective option for simple UTI caused by A. urinae 3
Treatment for Severe or Invasive Infections
- Penicillin or amoxicillin combined with gentamicin should be used for serious infections including endocarditis, bacteremia, or spondylodiscitis 1, 2, 4
- Time-kill studies demonstrate that penicillin or vancomycin alone exhibit slow or no bactericidal activity, but when combined with gentamicin, rapid bactericidal activity is achieved 1
- For invasive infections, intravenous amoxicillin for 14 days followed by oral therapy has been successfully used, as demonstrated in spondylodiscitis cases 4
Alternative Regimens
- Vancomycin combined with gentamicin represents the most appropriate alternative in penicillin-allergic patients with severe infections 1, 2
- Levofloxacin may be considered as step-down oral therapy after initial intravenous treatment for invasive infections, though quinolone susceptibility data are limited 4, 5
Treatment Duration
- 7 days for uncomplicated UTI 3
- 14 days of intravenous therapy followed by 3 months of oral therapy for spondylodiscitis 4
- Extended therapy (4-6 weeks) should be considered for endocarditis, following standard endocarditis treatment principles 2
Critical Pitfalls to Avoid
- Do not rely on empiric therapy without culture confirmation, as A. urinae is easily misidentified as streptococci or staphylococci on Gram stain, and cultures require CO2-containing atmosphere for optimal growth 4, 5
- Always obtain antibiotic susceptibility testing due to increasing antibiotic resistance patterns and uncertainty about the effectiveness of trimethoprim-sulfamethoxazole and fluoroquinolones against aerococci 3, 5
- Do not use monotherapy for severe infections such as endocarditis or bacteremia, as combination therapy with an aminoglycoside is essential for bactericidal activity 1, 2
- Recognize high-risk populations: A. urinae primarily affects older men (typically >65 years) with underlying urinary tract abnormalities, chronic urinary retention, indwelling catheters, diabetes, or history of urological surgery 3, 4, 5
Monitoring Recommendations
- Close monitoring of clinical status and laboratory results is essential during treatment of serious A. urinae infections to detect progression or complications 2
- Prompt and culture-specific treatment is critical to avoid clinical progression, particularly in patients with multimorbidity or urologic malignancies 3