From the Guidelines
No, Merrem (meropenem) does not adequately cover penicillin-sensitive Enterococcus faecalis. While meropenem is a broad-spectrum carbapenem antibiotic effective against many gram-positive and gram-negative bacteria, it has poor activity against enterococci, including penicillin-sensitive E. faecalis 1. For penicillin-sensitive E. faecalis infections, preferred antibiotics include ampicillin, penicillin G, or amoxicillin, often at high doses.
Key Points to Consider
- For more serious infections like endocarditis or bacteremia, combination therapy with an aminoglycoside (such as gentamicin) may be recommended for synergistic killing, as outlined in the 2015 ESC guidelines for the management of infective endocarditis 1.
- In penicillin-allergic patients, vancomycin is typically used as an alternative.
- The reason meropenem lacks activity against enterococci relates to its binding affinity for penicillin-binding proteins in enterococci, which differs from its activity against other gram-positive organisms.
- When treating suspected or confirmed E. faecalis infections, it's essential to select antibiotics with known activity against this organism rather than relying on carbapenem coverage.
Treatment Recommendations
- Ampicillin or amoxicillin are preferred for treating penicillin-sensitive E. faecalis infections, with or without the addition of an aminoglycoside for synergistic effects.
- Meropenem is not recommended as a first-line treatment for E. faecalis infections due to its limited activity against this organism.
- The most recent guidelines, such as those from the WHO's essential medicines and AWaRe recommendations, prioritize amoxicillin-clavulanic acid or cephalosporins with metronidazole for non-severe infections, and reserve carbapenems like meropenem for severe cases or when local resistance patterns warrant their use 1.
From the FDA Drug Label
Meropenem for injection is indicated for the treatment of complicated skin and skin structure infections (cSSSI) due to ... Enterococcus faecalis (vancomycin-susceptible isolates only)
Table 8: Clinical Efficacy Rates by Pathogen for Clinically Evaluable Population MICROORGANISMS1Meropenem for Injection n 2/N 3(%) 4 Enterococcus faecalis9/12 (75)
The FDA drug label does not explicitly state that merrem covers penicillin sensitive Enterococcus faecalis, it only mentions vancomycin-susceptible isolates of Enterococcus faecalis. Therefore, no conclusion can be drawn about penicillin sensitive Enterococcus faecalis. 2 2
From the Research
Merrem Coverage for Penicillin-Sensitive Enterococcus faecalis
- Meropenem (Merrem) is a broad-spectrum antibacterial agent with activity against Gram-positive and Gram-negative pathogens, including Enterobacteriaceae 3.
- However, the study from 2007 states that carbapenems, including meropenem, lack activity against Enterococcus faecium, but it does not explicitly mention Enterococcus faecalis 4.
- A study from 2022 found that meropenem plus ceftaroline demonstrated significant kill against penicillin-susceptible E. faecalis strains, with no regrowth or MIC increases occurring 5.
- Another study from 2023 found that meropenem plus ceftriaxone or ertapenem plus ceftriaxone demonstrated synergistic activity against E. faecalis strains, including those with reduced penicillin susceptibility 6.
- It is worth noting that the standard of care for serious E. faecalis infections is ampicillin plus ceftriaxone, but meropenem-based combination therapy may provide an alternative option 5, 7.
Key Findings
- Meropenem has broad-spectrum activity, but its effectiveness against E. faecalis is not well-established 3, 4.
- Combination therapy with meropenem and ceftaroline or ceftriaxone may be effective against E. faecalis 5, 6.
- Further studies are needed to determine the clinical efficacy of meropenem-based combination therapy for E. faecalis infections 5, 7.