Treatment of Prostatitis Caused by Enterococcus Faecalis with MIC 0.25
Amoxicillin 1 gram three times daily is an acceptable treatment for prostatitis caused by Enterococcus faecalis with a MIC of 0.25, as this dosage provides adequate tissue penetration and exceeds the minimum inhibitory concentration required for this susceptible strain. 1
Rationale for Amoxicillin Selection
- E. faecalis with MIC of 0.25 μg/mL is considered fully penicillin-susceptible (penicillin-susceptible defined as MIC ≤8 mg/L) 2
- Amoxicillin is preferred over other penicillins for enterococcal infections because MICs are typically two to four times lower than penicillin G 2
- High-dose amoxicillin regimens are necessary to achieve adequate prostatic tissue concentrations due to the relative impermeability of the prostate gland 1, 3
Dosing Considerations
- The recommended 1 gram TID dosing provides sufficient drug concentration to exceed the MIC of 0.25 μg/mL by a significant margin 1
- For chronic bacterial prostatitis, extended therapy duration of 4-6 weeks is typically required for complete eradication 3, 4
- The prostatic penetration of beta-lactams is limited in chronic prostatitis, but the high dosage (3 grams daily) helps overcome this limitation 3, 5
Alternative Regimens
- For patients with severe infections or treatment failure, combination therapy with ampicillin plus ceftriaxone may be considered 1
- For penicillin-allergic patients, fluoroquinolones (levofloxacin or ciprofloxacin) may be used as they have shown low resistance rates (4.8-9.7%) against E. faecalis in prostatitis 6
- Vancomycin is an alternative for patients with severe penicillin allergy but should be reserved for such cases due to stewardship concerns 2, 1
Monitoring and Follow-up
- Clinical response should be assessed after 2 weeks of therapy 7
- Complete microbiological cure requires 4-6 weeks of treatment for chronic bacterial prostatitis 7, 4
- Follow-up cultures of expressed prostatic secretions should be obtained after completion of therapy to confirm eradication 4
Important Considerations
- E. faecalis strains may produce beta-lactamase that is not detected by routine testing; however, with MIC of 0.25, this is unlikely to be clinically significant 2
- Aminoglycoside combination therapy, traditionally used for enterococcal endocarditis, is not necessary for uncomplicated prostatitis with a susceptible strain (MIC 0.25) 2, 1
- Treatment failure may occur due to poor prostatic penetration of beta-lactams, requiring reassessment and potential switch to alternative agents 3