Aerococcus urinae is Not Susceptible to Cephalexin
Aerococcus urinae is not susceptible to cephalexin and should be treated with other antibiotics such as penicillin, amoxicillin, or nitrofurantoin.
Antimicrobial Susceptibility of Aerococcus urinae
- Aerococcus urinae shows high susceptibility to penicillin, amoxicillin, meropenem, vancomycin, and nitrofurantoin, with susceptibility rates of 100% for most of these agents 1
- First-generation cephalosporins like cephalexin have poor activity against Aerococcus urinae and should not be used for treatment 2
- In vitro studies demonstrate that A. urinae isolates have low MICs (high susceptibility) to penicillin, amoxicillin, piperacillin, cefepime, vancomycin, and rifampicin 3
Recommended Treatment Options for A. urinae Infections
- For uncomplicated A. urinae UTIs, penicillin, amoxicillin, and nitrofurantoin are the preferred treatment options 2
- For severe infections such as bacteremia or endocarditis caused by A. urinae, combination therapy with penicillin or vancomycin plus gentamicin is recommended due to their synergistic bactericidal activity 3
- All 120 A. urinae isolates in a large study were found susceptible to penicillin, cefotaxime, meropenem, vancomycin, linezolid, and rifampicin 4
Important Clinical Considerations
- Aerococcus urinae is an emerging uropathogen that primarily affects elderly patients with underlying urological conditions 1
- Urine culture with susceptibility testing is essential for proper diagnosis and treatment of A. urinae infections due to potential antimicrobial resistance 2
- A. urinae can cause not only UTIs but also more severe infections like bacteremia and endocarditis, particularly in elderly patients with multimorbidity 5
Cephalexin Limitations and Pitfalls
- Cephalexin has been documented to have high resistance rates (96%) against certain organisms, making it an inappropriate choice for A. urinae 6
- First-generation cephalosporins like cephalexin should be avoided for empiric treatment when A. urinae is suspected 7
- When treating UTIs, it's essential to know local patterns of susceptibility to antimicrobial agents, particularly for drugs like cephalexin, due to substantial geographic variability 6
Alternative Treatment Approaches
- For patients with penicillin allergy, vancomycin (potentially combined with gentamicin for severe infections) represents the most obvious alternative 3
- Fluoroquinolones like ciprofloxacin and levofloxacin show good activity against A. urinae with susceptibility rates of 83.3% and 79.2%, respectively 1
- For complicated UTIs, obtain urine culture and susceptibility testing before initiating therapy to guide appropriate antibiotic selection 7