Is ertapenem (a carbapenem antibiotic) effective for treating spondylodiskitis?

Ertapenem for Spondylodiskitis

Ertapenem is an effective treatment option for spondylodiskitis, particularly when Enterobacteriaceae or anaerobic bacteria are involved, with good bone tissue penetration that exceeds the MIC90 for most relevant pathogens. 1

Rationale for Using Ertapenem in Spondylodiskitis

Ertapenem is a Group 1 carbapenem with several characteristics that make it suitable for treating bone and joint infections:

• Achieves good bone penetration with concentrations in cancellous bone (median 13.2 μg/g at 1.6 hours post-dose) and cortical bone (median 8.0 μg/g) that exceed the MIC90 for most susceptible pathogens 1
• Has a long half-life of 4.5 hours allowing for once-daily dosing 2
• Demonstrates broad-spectrum activity against many Gram-positive, Gram-negative, and anaerobic bacteria commonly involved in bone infections 3

Antimicrobial Spectrum Relevant to Spondylodiskitis

Ertapenem is particularly effective against:

• Enterobacteriaceae (MIC90s < 1 mg/L) 3
• Anaerobic bacteria including Bacteroides fragilis group (MIC90s 1-4 mg/L) 3
• Streptococci and methicillin-susceptible Staphylococcus aureus 3

However, ertapenem has limited activity against:

• Pseudomonas aeruginosa
• Acinetobacter species
• Methicillin-resistant staphylococci
• Enterococci 3

Evidence Supporting Use in Bone Infections

While specific randomized controlled trials for spondylodiskitis are limited, several lines of evidence support ertapenem use:

1. Pharmacokinetic studies demonstrate that ertapenem concentrations in bone tissue remain above the MIC90 for most relevant pathogens for 24 hours after a single 1g dose 1

2. The IWGDF/IDSA guidelines (2023) list carbapenems, including ertapenem, as effective options for treating diabetic foot osteomyelitis, which shares microbiological similarities with spondylodiskitis 4

3. Ertapenem has demonstrated clinical efficacy in complicated skin and skin structure infections, which can involve bone 5

Dosing Recommendations

• Standard dose: 1g once daily intravenously 5, 6
• Duration: Typically 4-6 weeks for vertebral osteomyelitis, though duration should be guided by clinical response and imaging findings

Advantages of Ertapenem for Spondylodiskitis

1. Once-daily dosing facilitates outpatient parenteral antibiotic therapy 6
2. Narrower spectrum than other carbapenems (imipenem, meropenem), reducing risk of developing resistance in non-target organisms 3
3. Stability against extended-spectrum beta-lactamases (ESBLs) and AmpC beta-lactamases 6
4. Good tissue penetration into bone and synovial tissues 1

Limitations and Considerations

• Not effective against Pseudomonas aeruginosa, which may be relevant in healthcare-associated spondylodiskitis 3
• Limited data specifically for spondylodiskitis compared to other indications
• Should be reserved for cases where narrower-spectrum agents are not appropriate, to prevent development of resistance

Patient Selection for Ertapenem

Ertapenem is most appropriate for:

• Community-acquired spondylodiskitis
• Infections likely caused by Enterobacteriaceae or anaerobes
• Patients requiring outpatient parenteral therapy
• Cases where once-daily dosing improves adherence or logistics

Monitoring During Treatment

• Clinical response (pain, neurological symptoms, inflammatory markers)
• Follow-up imaging to assess structural improvement
• Renal function monitoring
• Surveillance for adverse effects (most commonly diarrhea, nausea, headache, infusion site reactions) 5

In conclusion, ertapenem represents a valuable option for treating spondylodiskitis, particularly for community-acquired infections where Enterobacteriaceae or anaerobic pathogens are suspected or confirmed. Its pharmacokinetic profile and bone penetration make it suitable for this indication, though microbiological guidance through culture results should direct definitive therapy whenever possible.