Duration of Oral Amoxicillin for E. faecalis Infection
For uncomplicated E. faecalis infections, treat with amoxicillin 500 mg orally every 8 hours for 7 days, which achieves high clinical (88.1%) and microbiological (86%) eradication rates. 1, 2
Treatment Duration by Clinical Context
Uncomplicated Urinary Tract Infections
- 7 days of amoxicillin 500 mg orally every 8 hours is the standard duration for uncomplicated UTIs caused by susceptible E. faecalis 1, 2
- This regimen is recommended by the American College of Physicians as first-line therapy 1, 2
- Ampicillin 500 mg orally every 8 hours for 7 days is an equivalent alternative with similar efficacy 1, 2
Uncomplicated Bloodstream Infections (Catheter-Related)
- 7-14 days of therapy is recommended for uncomplicated enterococcal catheter-related bloodstream infections when the catheter is removed 3, 2
- Recent evidence from a multicenter cohort suggests that 7 days may be sufficient for non-complicated enterococcal central line-associated bloodstream infections when the catheter is removed promptly (within median 3 days) 4
- The shorter 7-day duration showed no increased 30-day mortality compared to longer courses in patients without endocarditis 4
When Longer Duration is Required
- Extend beyond 7-14 days if any of the following are present: 3, 2
- Signs of endocarditis (new murmur, embolic phenomena)
- Persistent bacteremia >72 hours despite appropriate therapy
- Metastatic infection sites
- Complicated UTI or pyelonephritis
- Prosthetic valve or endovascular foreign bodies present
Critical Pre-Treatment Considerations
Susceptibility Testing is Mandatory
- Always obtain culture and susceptibility testing before initiating amoxicillin, even for strains described as "pansensitive" 1, 2
- Approximately 2% of E. faecalis are vancomycin-resistant with variable ampicillin susceptibility 3, 2
- Ampicillin/amoxicillin is the drug of choice only for ampicillin-susceptible enterococci 3
Differentiate Colonization from Infection
- Confirm true infection rather than asymptomatic bacteriuria before prescribing anti-enterococcal agents 1
- Asymptomatic bacteriuria with E. faecalis does not routinely require treatment 1
Common Pitfalls to Avoid
Risk of Relapse with Shorter Courses
- A 4-week course appears insufficient for complicated infections: In endocarditis, relapses were significantly more frequent with 4 weeks (17%) versus 6 weeks (2%) of treatment 5
- Three of four relapses occurred in cirrhotic patients, suggesting avoid shorter durations in patients with cirrhosis 5
Do Not Extend Duration Without Indication
- Avoid extending treatment beyond 7 days for uncomplicated UTI without clear clinical indication, as this increases antibiotic resistance risk without proven benefit 2
- The 7-14 day range for catheter-related infections should be based on clinical response and source control 3
Evaluate for Endocarditis
- Perform transesophageal echocardiography (TEE) if bacteremia persists >72 hours, as enterococcal bacteremia persisting >4 days is independently associated with mortality 3
- The risk of endocarditis is relatively low (1.5% in one multicenter study) but must be excluded in high-risk scenarios 3
Alternative Oral Agents (When Amoxicillin Cannot Be Used)
- Nitrofurantoin 100 mg orally every 6 hours for 7 days has good activity against E. faecalis with resistance rates <6% 1, 2
- Fosfomycin 3 g orally as a single dose is FDA-approved specifically for UTI caused by E. faecalis and recommended for uncomplicated infections 1, 2
- Fluoroquinolones should be avoided due to high resistance rates (46-47%) 1, 2