What antibiotics are recommended for coverage against Corynebacterium and Enterococcus (E) faecalis?

Antibiotic Coverage for Corynebacterium and E. faecalis

For Corynebacterium species, vancomycin is the drug of choice, while for E. faecalis, ampicillin remains first-line therapy when susceptible, with vancomycin, piperacillin-tazobactam, or linezolid as alternatives based on resistance patterns and infection severity. 1, 2

Coverage for Corynebacterium

Vancomycin is the definitive treatment for serious Corynebacterium infections, particularly corynebacterial endocarditis and other invasive infections caused by organisms resistant to commonly used agents 2.

• Vancomycin demonstrates excellent activity against Corynebacterium species (diphtheroids) with bactericidal action 3, 4
• Standard dosing is 1 g IV every 12 hours in patients with normal renal function, maintaining serum levels ≤30 mcg/mL to minimize neurotoxicity 2
• Vancomycin inhibits cell wall synthesis and alters bacterial cell membrane permeability, providing reliable coverage against these gram-positive bacilli 3

Coverage for Enterococcus faecalis

The antibiotic selection for E. faecalis depends critically on the clinical context (community-acquired vs. healthcare-associated) and resistance patterns:

For Susceptible E. faecalis (Community Settings)

Ampicillin is the drug of choice for enterococcal infections when the organism remains susceptible 1:

• Ampicillin can be used at standard doses for most infections 1
• For serious infections like endocarditis, ampicillin combined with an aminoglycoside (gentamicin) provides synergistic bactericidal activity 2, 3
• Piperacillin-tazobactam provides effective coverage and can be used as an alternative based on susceptibility testing 1

For Healthcare-Associated or Resistant E. faecalis

Empiric anti-enterococcal therapy is recommended for healthcare-associated intra-abdominal infections, postoperative infections, patients with prior cephalosporin exposure, immunocompromised patients, and those with valvular heart disease or prosthetic intravascular materials 1:

• Linezolid 600 mg IV or PO every 12 hours is strongly recommended for enterococcal infections, particularly when vancomycin resistance is present 1
• Vancomycin remains an option for vancomycin-susceptible E. faecalis based on susceptibility testing 1
• For serious VRE infections, high-dose daptomycin (8-12 mg/kg/day) is preferred due to its bactericidal activity, with combination therapy (adding β-lactams including penicillins, cephalosporins, or carbapenems) recommended for VRE bacteremia 1

Site-Specific Considerations

For intra-abdominal infections with polymicrobial flora:

• Tigecycline (100 mg IV loading dose, then 50 mg IV every 12 hours) is recommended for polymicrobial infections including VRE 1
• Linezolid is preferred for monomicrobial enterococcal infections 1

For uncomplicated urinary tract infections due to VRE:

• Single-dose fosfomycin 3 g PO is recommended 1
• Nitrofurantoin 100 mg PO every 6 hours provides effective coverage 1
• High-dose ampicillin (18-30 g IV daily) may overcome resistance in UTIs due to high urinary concentrations 1

Critical Clinical Pitfalls

• Do not use ceftaroline for VRE - despite activity against other gram-positive organisms, it has poor activity against enterococci 1
• Differentiate colonization from true infection before initiating anti-VRE therapy, as unnecessary broad-spectrum coverage drives further resistance 1
• Empiric enterococcal coverage is NOT recommended for community-acquired intra-abdominal infections unless specific risk factors are present 1
• For vancomycin use, monitor serum levels to prevent neurotoxicity (keep ≤30 mcg/mL) 2
• Linezolid therapy >14-21 days carries risk of thrombocytopenia requiring monitoring 5

Combination Therapy Considerations

Vancomycin combined with aminoglycosides demonstrates synergistic activity against enterococci, particularly for endocarditis 2, 3, 4:

• This combination is essential for enterococcal endocarditis when using vancomycin in penicillin-intolerant patients 2
• Vancomycin should not be used alone for enterococcal endocarditis 2
• For non-enterococcal streptococcal endocarditis, vancomycin may be used alone if the minimum bactericidal concentration is ≤10 mcg/mL 2