Would amoxicillin (amoxicillin) 1gm three times a day (TID) orally (po) be effective for treating prostatitis caused by Enterococcus Faecalis with a minimum inhibitory concentration (MIC) sensitivity of 0.50 to amoxicillin?

Treatment of Prostatitis Caused by Enterococcus Faecalis with MIC 0.50 to Amoxicillin

Amoxicillin 1 gram TID orally is an effective and appropriate dosage for treating prostatitis caused by Enterococcus faecalis with an MIC of 0.50 to amoxicillin. 1

Rationale for Amoxicillin Selection

• Amoxicillin is preferred over other penicillins for enterococcal infections because MICs are typically two to four times lower than penicillin G 1
• E. faecalis with MIC of 0.50 μg/mL is considered fully susceptible to penicillin/amoxicillin, as the susceptibility breakpoint is ≤8 mg/L 1
• High-dose amoxicillin is specifically recommended for chronic prostatitis caused by E. faecalis according to clinical guidelines 1

Dosing Considerations

• The recommended dose of 1 gram TID (3 grams daily) exceeds the standard dose of 500 mg every 8 hours mentioned in some guidelines, which is appropriate for ensuring adequate prostatic tissue penetration 1
• Higher doses are necessary because the prostate has a physiological barrier that limits antibiotic penetration, particularly in chronic infections 2
• The proposed dose of 1 gram TID is appropriate to achieve sufficient concentrations in prostatic tissue while remaining within safe dosing parameters 1

Treatment Duration

• Extended therapy (4-16 weeks) is typically required for bacterial prostatitis to ensure complete eradication 3
• A minimum treatment duration of 4-6 weeks is recommended for enterococcal infections to prevent relapse 1
• Regular follow-up cultures may be necessary to confirm eradication 4

Alternative Regimens

• For patients with severe infections or treatment failure, consider:
  • Ampicillin 2 g IV every 4 hours combined with ceftriaxone 2 g IV every 12 hours 1
  • For penicillin-allergic patients, vancomycin 30 mg/kg/day IV in 2 divided doses can be substituted 1

Important Clinical Considerations

• E. faecalis strains may occasionally produce beta-lactamase that is not detected by routine testing; however, with an MIC of 0.50, this is unlikely to be clinically significant 5
• Fluoroquinolones have traditionally been used for prostatitis but resistance rates of approximately 9.7% for ciprofloxacin and 4.8% for levofloxacin have been reported in E. faecalis strains from prostatitis 6
• Avoid tetracycline, erythromycin, and trimethoprim/sulfamethoxazole due to high resistance rates (97.5%, 95%, and 31.5% respectively) in E. faecalis isolates from prostatitis 6

Monitoring

• Regular monitoring of clinical response is essential, with consideration of repeat cultures if symptoms persist 4
• Monitor for potential hypersensitivity reactions to β-lactams 1
• If treatment failure occurs, consider:
  • Longer duration of therapy
  • Higher dosage
  • Alternative antibiotics based on updated susceptibility testing 4