This patient should receive ampicillin in place of meropenem. Distinguishing between bacteremia caused by E. faecalis versus Enterococcus faecium is necessary because E. faecium is relatively more resistant than E. faecalis and more likely to be vancomycin resistant, depending on local epidemiology. Intravenous ampicillin is the most appropriate treatment option for sensitive E. faecalis because it is the most narrow-spectrum agent and antibiotic of choice for this organism. Antibiotic stewardship requires that empiric antimicrobial therapy be modified or de-escalated as soon as culture results are available, even when a patient is improving with the empiric antimicrobial regimen. Doing so helps preserve the effectiveness of broad-spectrum agents used to initially treat patients requiring aggressive therapy. Meropenem is highly effective against a wide range of organisms, and this breadth of coverage is unnecessary after the primary infecting organism has been identified. Additionally, it is less active against E. faecalis than ampicillin or vancomycin and should therefore be discontinued.

Adding gentamicin to ampicillin or vancomycin is not necessary in nonendocarditis E. faecalis infections, including bacteremia. In this patient, E. faecalis bacteremia occurred secondary to urinary tract infection; he has no evidence of endocarditis by history, examination, or clinical course. In patients with enterococcal endocarditis, adding gentamicin (if high-level aminoglycoside resistance is not present) to ampicillin or vancomycin for a limited period early in the treatment course improves clinical outcomes.

Vancomycin is used in patients who are allergic to penicillin or in ampicillin-resistant E. faecalis but is not the initial agent of choice for use against E. faecalis.