Does ertapenem provide coverage against Pseudomonas aeruginosa?

Ertapenem Does Not Provide Coverage Against Pseudomonas aeruginosa

Ertapenem does not have activity against Pseudomonas aeruginosa and should not be used when coverage for this pathogen is required. 1

Classification and Spectrum of Activity

• Ertapenem is a Group 1 carbapenem antibiotic with a broad spectrum of activity against many Gram-positive and Gram-negative bacteria, but it specifically lacks activity against Pseudomonas aeruginosa 1, 2
• Carbapenems are classified into different groups based on their antimicrobial spectrum:
  • Group 1 carbapenems (ertapenem): Active against extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae but NOT active against Pseudomonas aeruginosa and Enterococcus species 1
  • Group 2 carbapenems (imipenem/cilastatin, meropenem, doripenem): Have activity against non-fermentative Gram-negative bacilli including Pseudomonas aeruginosa 1

Evidence Supporting Lack of Pseudomonal Coverage

• The 2017 World Society of Emergency Surgery (WSES) guidelines explicitly state that ertapenem "has activity against extended-spectrum beta-lactamase (ESBL)-producing pathogens, but not active against P. aeruginosa and Enterococcus species" 1
• In vitro studies confirm that ertapenem has "restricted activity against nosocomial pathogens such as Pseudomonas aeruginosa, Acinetobacter species, methicillin-resistant staphylococci and enterococci" 2
• When tested against P. aeruginosa isolates from intensive care units, ertapenem demonstrated less activity compared to other carbapenems like imipenem and meropenem 3

Clinical Implications and Recommendations

• For infections where Pseudomonas aeruginosa is a concern:

  • Use Group 2 carbapenems (imipenem, meropenem, doripenem) instead of ertapenem 1
  • Alternative anti-pseudomonal options include antipseudomonal cephalosporins (ceftazidime, cefepime), piperacillin-tazobactam, aminoglycosides, or ciprofloxacin/levofloxacin 1

• For hospital-acquired or ventilator-associated pneumonia where P. aeruginosa is a concern:

  • Ertapenem should only be used in combination with specific anti-pseudomonal agents when P. aeruginosa coverage is needed 4
  • For patients at risk of P. aeruginosa infection, guidelines recommend antipseudomonal cephalosporins, acylureidopenicillin/β-lactamase inhibitors, or Group 2 carbapenems plus either ciprofloxacin or a macrolide with an aminoglycoside 1

Common Pitfalls and Caveats

• Ertapenem is often mistakenly grouped with other carbapenems regarding its spectrum of activity, but it critically lacks pseudomonal coverage 1, 2
• While ertapenem can select for P. aeruginosa mutants with cross-resistance to other carbapenems in vitro, clinical studies have not shown that ertapenem use decreases Pseudomonas susceptibility to antipseudomonal carbapenems 5, 6
• Ertapenem remains an appropriate choice for community-acquired infections where ESBL-producing Enterobacteriaceae are a concern but Pseudomonas aeruginosa is unlikely 1
• Using ertapenem appropriately (when P. aeruginosa is not a concern) may help preserve the activity of Group 2 carbapenems by reducing selection pressure 1, 5