Treatment of Aerococcus urinae Urinary Tract Infection
For uncomplicated cystitis caused by Aerococcus urinae, nitrofurantoin is the first-line treatment, achieving clinical and microbiological cure in 71% and 76% of cases respectively. 1
Initial Diagnostic Approach
- Obtain urine culture with antibiotic susceptibility testing before initiating therapy, as Aerococcus species have variable resistance patterns and are frequently misidentified as streptococci or staphylococci on routine culture. 2, 3
- Remove any indwelling urinary catheters immediately if present, as catheterization is a major risk factor for aerococcal UTI. 4
- Recognize that Aerococcus urinae primarily affects older adults (median age 82 years) with multimorbidity, chronic urinary retention, or urologic abnormalities. 5, 2
Treatment Regimens by Clinical Presentation
Uncomplicated Cystitis (Lower UTI)
- Nitrofurantoin 100 mg orally every 6 hours for 5-7 days is the preferred first-line agent for A. urinae cystitis, with proven clinical effectiveness. 1, 4
- Pivmecillinam is an effective alternative specifically for A. urinae cystitis based on prospective treatment data. 1
- Amoxicillin or penicillin are also appropriate options given the organism's susceptibility profile. 2, 5
Complicated UTI or Pyelonephritis
- Ciprofloxacin 400 mg IV every 12 hours achieved treatment success in patients with pyelonephritis caused by A. urinae in prospective studies. 1
- For complicated UTI with systemic symptoms, use amoxicillin plus an aminoglycoside, or a second/third-generation cephalosporin as empirical treatment per standard complicated UTI guidelines. 4
- Ceftriaxone, penicillin G, and vancomycin demonstrate excellent in vitro susceptibility against both A. urinae and A. sanguinicola isolates. 5
- Treatment duration should be 7-14 days for complicated UTI (14 days for men when prostatitis cannot be excluded). 4
Invasive Infections (Bacteremia/Urosepsis)
- Penicillin is the appropriate treatment for invasive aerococcal infections, with addition of an aminoglycoside for infective endocarditis. 3
- Untreated A. urinae infections can progress to urosepsis, making prompt culture-specific treatment critical. 5, 2
- For bacteremia without endocarditis, the prognosis is favorable with appropriate antibiotic therapy. 3
Critical Pitfalls to Avoid
- Do not rely on trimethoprim-sulfamethoxazole or fluoroquinolones without susceptibility testing, as their effectiveness against aerococci remains uncertain despite in vitro susceptibility. 3
- Do not treat asymptomatic bacteriuria with A. urinae in non-pregnant patients, as this fosters resistance without clinical benefit. 4
- Ensure cultures are incubated in CO2-containing atmosphere, as aerococci may not grow under standard urine culture conditions, leading to underdiagnosis. 6
- Recognize that A. sanguinicola has lower treatment success rates with nitrofurantoin (42% clinical cure, 50% microbiological cure) compared to A. urinae, requiring alternative agents. 1
Antimicrobial Susceptibility Profile
- A. urinae and A. sanguinicola demonstrate consistent susceptibility to penicillin, amoxicillin, ceftriaxone, and vancomycin. 5, 2
- Increasing antibiotic resistance patterns necessitate culture-specific treatment rather than empirical therapy alone. 2
- MALDI-TOF mass spectrometry provides rapid and accurate identification, improving diagnostic accuracy over traditional methods. 3