From the Guidelines
No, ceftriaxone does not effectively cover enterococcus as a single agent, but it can be used in combination with ampicillin for certain enterococcal strains. Ceftriaxone is a third-generation cephalosporin that has good activity against many gram-negative organisms and some gram-positive bacteria, but it has poor activity against enterococci (including Enterococcus faecalis and Enterococcus faecium) when used alone 1. If enterococcal coverage is needed, more appropriate antibiotic choices would include ampicillin (for ampicillin-sensitive enterococci), vancomycin (for ampicillin-resistant strains), or combination therapy with ampicillin plus an aminoglycoside for synergistic effect in serious infections.
Key Points to Consider
- The combination of ampicillin plus ceftriaxone was reported to be effective for aminoglycoside nonsusceptible Enterococcus faecalis strains 1.
- Enterococci are resistant to ceftriaxone and other cephalosporins, and these drugs used alone are not an option for treatment of enterococcal endocarditis 1.
- For vancomycin-resistant enterococci (VRE), options include linezolid, daptomycin, or tigecycline depending on the specific situation and susceptibility patterns.
Treatment Recommendations
- For gentamicin-resistant and streptomycin-susceptible Enterococcus species, ampicillin-ceftriaxone combination therapy is reasonable (Class IIa; Level of Evidence B) 1.
- Six weeks of therapy is reasonable if ampicillin plus ceftriaxone is selected as the treatment regimen, regardless of symptom duration (Class IIa; Level of Evidence B) 1.
From the Research
Ceftriaxone Coverage of Enterococcus
- Ceftriaxone has been studied in combination with other antibiotics for the treatment of Enterococcus faecalis infections, including infective endocarditis 2, 3, 4, 5.
- The combination of ceftriaxone and ampicillin has been proposed as an alternative treatment for Enterococcus faecalis infective endocarditis in outpatient parenteral antibiotic therapy programs 3, 5.
- However, the efficacy of ceftriaxone against Enterococcus faecalis is not well established, and its use as a single agent is not recommended 6, 4.
- Synergistic effects of penicillin and ceftriaxone against E. faecalis have been observed in some studies, but the relationship between ceftriaxone susceptibility and penicillin/ceftriaxone synergy is not fully understood 2.
- Ceftriaxone has been shown to be effective against some Gram-positive bacteria, but its activity against Enterococcus faecalis is generally less than that of other cephalosporins 6.
Limitations of Ceftriaxone for Enterococcus Treatment
- Ceftriaxone may not be effective against all strains of Enterococcus faecalis, particularly those with high MICs 2, 3.
- The use of ceftriaxone in combination with ampicillin may promote colonization with vancomycin-resistant enterococci due to high biliary concentrations 4.
- More research is needed to determine the optimal treatment regimen for Enterococcus faecalis infections, including the role of ceftriaxone in combination therapy 4, 5.