Antibiotic Treatment for Enterococcus faecium Infections

First-Line Treatment Algorithm

The American College of Cardiology is not applicable here, however, for ampicillin-susceptible E. faecium, ampicillin is recommended as first-line therapy 1
For vancomycin-susceptible but ampicillin-resistant E. faecium, vancomycin is used 2, 3
For vancomycin-resistant E. faecium (VRE), linezolid 600 mg IV/PO every 12 hours is recommended 4

Daptomycin 8-12 mg/kg/day IV is recommended as an alternative for VRE bacteremia 4
Quinupristin-dalfopristin (Synercid) inhibits growth only in E. faecium (not E. faecalis) 2
Tigecycline 100 mg IV loading dose followed by 50 mg IV every 12 hours for intra-abdominal infections 4, 5

E. faecium is more likely to be resistant to multiple antibiotics compared to E. faecalis 1, 6
Five phenotypes of vancomycin resistance (vanA through E) exist in enterococci, with vanA and vanB genes found primarily in E. faecium 2, 3
Vancomycin-resistant E. faecium is often multidrug-resistant, creating significant treatment challenges 2

For severe VRE infections, consider combination therapy with daptomycin plus ampicillin or ceftaroline for potential synergistic effects 1
Double β-lactam combinations (imipenem and ampicillin or cephalosporins plus ampicillin) have shown synergistic bactericidal activity against some E. faecalis strains 2, 3

For uncomplicated VRE urinary tract infections, consider fosfomycin 3 g PO single dose 4
For uncomplicated VRE urinary tract infections, consider nitrofurantoin 100 mg PO every 6 hours 4
For uncomplicated VRE urinary tract infections, consider high-dose ampicillin (18-30 g IV daily in divided doses) or amoxicillin 500 mg PO/IV every 8 hours if susceptible 4
For endocarditis caused by vancomycin-resistant E. faecium, linezolid therapy resulted in cure of 77% of cases 2, 3
Daptomycin at higher doses (10-12 mg/kg/day) may be more effective for serious infections like endocarditis 1

Monitor for bone marrow suppression and neuropathy with prolonged linezolid use 1
Enterococci are intrinsically resistant to cephalosporins when used as monotherapy 1

The American Heart Association recommends linezolid as one of the two available antimicrobial agents in the United States for the treatment of multiresistant E. faecium, with a susceptibility rate of 97-99% for these multiresistant strains 7, 8
Most E. faecium strains resistant to vancomycin (up to 95%) express multiple resistance to vancomycin, aminoglycosides, and penicillins 8

For severe infections such as endocarditis caused by vancomycin-resistant E. faecium, a treatment duration of at least 6 weeks is recommended 9
Daptomicina at high doses (8-12 mg/kg/day) may be considered as an alternative for vancomycin-resistant E. faecium infections 9
Quinupristina-dalfopristina may be active in vitro against E. faecium, but is rarely used due to severe side effects 8

The American College of Microbiology recommends tigecycline 100 mg IV loading dose, then 50 mg IV every 12 hours for intra-abdominal infections when standard agents have failed, with a weak recommendation and very low quality evidence (2D) 10, 11
The Infectious Diseases Society of America suggests duration of treatment for 5-7 days based on clinical response and source control for intra-abdominal infections 11
For urinary tract infections, the European Society of Clinical Microbiology and Infectious Diseases recommends fosfomycin 3 g PO single dose or every other day for resistant strains, and nitrofurantoin 100 mg PO every 6 hours for 3-7 days 10, 11, 12
High-dose ampicillin 18-30 g IV daily in divided doses is recommended if susceptibility testing shows sensitivity, and amoxicillin 500 mg PO/IV every 8 hours if ampicillin-susceptible 10, 11

The Centers for Disease Control and Prevention emphasizes that species identification is mandatory, with quinupristin-dalfopristin being an option for E. faecium but not E. faecalis 10, 11
The World Health Organization notes that infection site determines options, with tigecycline being the guideline-supported choice for intra-abdominal infections, and multiple oral options available for urinary tract infections 10, 11

The American College of Microbiology advises that treatment duration should be individualized, with 5-7 days for uncomplicated UTI, 10-14 days for bacteremia, and at least 6 weeks for endocarditis 10, 11
The Infectious Diseases Society of America recommends monitoring clinical response closely given the limited evidence base for these salvage regimens, and infectious diseases consultation is strongly advised for all cases of multiply-resistant VRE 10, 11