From the Guidelines
Ampicillin is the best antibiotic for treating Enterococcus faecalis infections, typically administered at 200 mg/kg/day i.v. in 4 –6 doses, in combination with gentamicin 3 mg/kg/day i.v. or i.m. in 1 dose, for 4-6 weeks. This recommendation is based on the 2015 ESC guidelines for the management of infective endocarditis 1. The combination of ampicillin and gentamicin is active against Enterococcus faecalis strains with and without high-level aminoglycoside resistance (HLAR), making it the combination of choice in patients with HLAR E. faecalis endocarditis.
Some key points to consider when treating E. faecalis infections include:
- Susceptibility testing is crucial before initiating treatment as resistance patterns vary
- E. faecalis has intrinsic resistance to many antibiotics, including cephalosporins and clindamycin, which should be avoided
- For patients with penicillin allergies, vancomycin is the preferred alternative, given at 30 mg/kg/day i.v. in 2 doses, in combination with gentamicin 3 mg/kg/day i.v. or i.m. in 1 dose, for 6 weeks
- Treatment duration varies based on infection site, with 4-6 weeks recommended for endocarditis or bone infections
- The effectiveness of ampicillin against E. faecalis stems from its ability to inhibit cell wall synthesis in this gram-positive organism, while the synergistic effect with aminoglycosides enhances bacterial killing, as supported by the American Heart Association guidelines 1.
It's worth noting that other studies, such as the 2005 American Heart Association statement 1, also provide guidance on treating Enterococcus faecalis infections, but the 2015 ESC guidelines provide the most recent and highest-quality evidence.
From the FDA Drug Label
Linezolid has been shown to be active against most isolates of the following microorganisms, both in vitro and in clinical infections... Aerobic and facultative Gram-positive microorganisms... Enterococcus faecalis (including vancomycin-resistant strains) Daptomycin has been shown to be active against most isolates of the following microorganisms both in vitro and in clinical infections... Gram-Positive Bacteria... Enterococcus faecalis (vancomycin-susceptible isolates only)
The best antibiotic for E. Faecalis is linezolid, as it is active against both vancomycin-susceptible and vancomycin-resistant strains of E. Faecalis 2. In contrast, daptomycin is only active against vancomycin-susceptible isolates of E. Faecalis 3.
From the Research
Antibiotic Options for E. Faecalis
- Aminopenicillins are preferred when E. faecalis is susceptible and patients can tolerate them 4
- Daptomycin and linezolid have demonstrated clinical efficacy against vancomycin-resistant enterococci (VRE) 4, 5, 6, 7
- Nitrofurantoin, fosfomycin, and doxycycline have intrinsic activity against enterococci, including VRE, and are possible oral options for VRE cystitis 5, 7
- Ampicillin is generally considered the drug of choice for ampicillin-susceptible enterococcal UTIs, including VRE 7
- Linezolid and daptomycin should be reserved for confirmed or suspected upper and/or bacteremic VRE UTIs among ampicillin-resistant strains 7
Considerations for Treatment
- The optimal therapy for E. faecalis infections is not well established and clinical data are usually limited to case reports with conflicting results 8
- Treatment decisions may have to be based on animal models and sporadic experiences, and the best approach is for the physician to consider carefully each patient on a case by case manner and gather all the clinical and microbiological information possible regarding species identification and susceptibilities 8
- Synergistic combinations are often warranted in complex infections of high inoculum and biofilms, while monotherapies are generally appropriate for uncomplicated infections 4