Treatment Approach for E. coli Superinfection During Enterococcus Faecalis Chronic Bacterial Prostatitis Therapy
Complete the remaining 2 weeks of amoxicillin as planned, then initiate levofloxacin monotherapy for the E. coli infection. This sequential approach optimizes cure of the nearly year-long enterococcal infection while addressing the new E. coli pathogen with appropriate targeted therapy.
Rationale for Sequential Therapy
Complete Enterococcal Treatment First
For enterococcal infections, ampicillin (or amoxicillin) should be given for one to two weeks intravenously followed by oral therapy with amoxicillin, with total treatment duration of 6 weeks considered sufficient after implant removal or source control 1.
You are 4 weeks into a 6-week course with documented clinical improvement and clearing cultures—this represents substantial progress in a difficult, nearly year-long case that warrants completion 1.
Premature discontinuation of amoxicillin risks relapse of the enterococcal infection, which has proven extremely difficult to eradicate over the past year 1.
Why Not Start Levofloxacin Concurrently
Fluoroquinolones should only be started after debridement and when wounds are dry, because of selection of resistance to fluoroquinolones when bioburden is high 1.
The presence of E. faecalis (even if not detected in the most recent culture) may still represent residual bioburden that could promote fluoroquinolone resistance development if levofloxacin is introduced prematurely 1.
Fluoroquinolone monotherapy against certain organisms is not recommended because of rapid emergence of resistance and high treatment failure rates 1.
Why Not Switch to Levofloxacin Immediately
Discontinuing amoxicillin now abandons 4 weeks of progress against a documented, difficult enterococcal infection that has persisted for nearly a year 1.
The E. coli may represent colonization or a secondary/superinfection rather than the primary pathogen requiring immediate treatment, especially given the clinical improvement on amoxicillin 1.
Levofloxacin has excellent activity on gram-negative bacterial biofilms and should be initiated after the primary infection is adequately treated 1.
Levofloxacin Dosing After Amoxicillin Completion
High-dose levofloxacin (750 mg daily) provides prolonged bactericidal activity against E. coli isolates, including those with elevated MICs 2.
Standard treatment duration for complicated urinary/prostatic infections is typically 4-6 weeks, though this should be guided by clinical response 2.
The E. coli's exquisite sensitivity to levofloxacin suggests excellent treatment prospects once initiated 2.
Critical Monitoring Points
Obtain repeat urine cultures at the end of the 6-week amoxicillin course before starting levofloxacin to confirm E. faecalis eradication and reassess E. coli presence 1.
If clinical deterioration occurs during the final 2 weeks of amoxicillin (fever, worsening symptoms, sepsis), this would necessitate immediate addition or switch to levofloxacin 1.
Recent hospitalization and prior fluoroquinolone use are significant risk factors for fluoroquinolone-resistant E. coli, though your isolate is currently sensitive 3, 4.
Important Caveats
This recommendation assumes the patient remains clinically stable with continued improvement on amoxicillin 1.
The correlation between levofloxacin consumption and fluoroquinolone-resistant E. coli is well-established, making judicious use and completion of the enterococcal therapy first a prudent antimicrobial stewardship approach 5.
If the E. coli represents true infection rather than colonization (evidenced by symptoms, pyuria, or clinical deterioration), earlier initiation of levofloxacin may be warranted 2.
Consider that the E. coli may have emerged due to disruption of normal flora by prolonged amoxicillin therapy, and may resolve spontaneously once antibiotics are completed 3.