What is the recommended management of a resistant gram‑negative infection in an adult ICU patient?

Management of Resistant Gram-Negative Infections in ICU Patients

For severe resistant gram-negative infections in ICU patients, prioritize newer beta-lactam/beta-lactamase inhibitor combinations (ceftazidime-avibactam or meropenem-vaborbactam for CRE; ceftolozane-tazobactam for resistant Pseudomonas) based on in vitro susceptibility, reserving cefiderocol for metallo-beta-lactamase producers resistant to all other options. 1

Carbapenem-Resistant Enterobacterales (CRE)

Severe Infections (including septic shock, bacteremia, pneumonia)

• First-line monotherapy: Use meropenem-vaborbactam or ceftazidime-avibactam if the organism is susceptible in vitro 1

  • These agents demonstrate moderate-quality evidence for efficacy in severe CRE infections
  • Do NOT add combination therapy when using these newer agents for susceptible organisms 1

• Metallo-beta-lactamase (MBL) producers: Use cefiderocol when organisms carry MBLs and/or are resistant to ceftazidime-avibactam and meropenem-vaborbactam 1

  • Alternative: Aztreonam plus ceftazidime-avibactam combination for MBL-producing CRE 1

• Pan-resistant CRE (susceptible only to older agents): Use combination therapy with two in vitro active drugs from polymyxins, aminoglycosides, tigecycline, or fosfomycin 1

  • Fosfomycin-containing combinations show potential mortality benefit (RR 0.55) though evidence quality is very low 1
  • Avoid tigecycline for bloodstream infections and pneumonia; if necessary for pneumonia, use high-dose tigecycline 1

Non-Severe CRE Infections

• Use older antibiotics active in vitro, selected individually based on infection source 1
• For complicated urinary tract infections: Prefer aminoglycosides (including plazomicin) over tigecycline 1

Carbapenem-Resistant Pseudomonas aeruginosa (CRPA/DTR-P. aeruginosa)

Severe Infections

• Preferred: Ceftolozane-tazobactam if active in vitro 1

  • Evidence for imipenem-relebactam, cefiderocol, and ceftazidime-avibactam remains insufficient at this time 1

• Pan-resistant CRPA: Use combination therapy with two in vitro active drugs when treating with polymyxins, aminoglycosides, or fosfomycin 1

  • Evidence quality is very low, but combination therapy is suggested over monotherapy for severe infections 1

Non-Severe CRPA Infections

• Monotherapy with older antibiotics active in vitro is appropriate, selected based on infection source and individual susceptibility 1

Third-Generation Cephalosporin-Resistant Enterobacterales (3GCephRE/ESBL)

Severe Infections and Bloodstream Infections

• Definitive therapy: Carbapenems (imipenem or meropenem) are strongly recommended 1
• Without septic shock: Ertapenem may be used instead of imipenem or meropenem 1

Non-Severe Infections

• Consider piperacillin-tazobactam, amoxicillin-clavulanate, or fluoroquinolones based on susceptibility 1
• For complicated UTI without septic shock: Aminoglycosides (short duration) or IV fosfomycin 1
• De-escalation: Once stabilized, step down from carbapenems to older beta-lactam/beta-lactamase inhibitors, fluoroquinolones, or cotrimoxazole based on susceptibility 1

Critical Antibiotic Stewardship Considerations

• Reserve newer beta-lactam/beta-lactamase inhibitors (ceftazidime-avibactam, meropenem-vaborbactam, ceftolozane-tazobactam) for extensively resistant organisms; avoid using them for 3GCephRE 1
• Do NOT use tigecycline for 3GCephRE infections 1
• Avoid cephamycins and cefepime for 3GCephRE 1

Essential Management Principles

Therapeutic Drug Monitoring (TDM)

• Perform TDM for aminoglycosides, polymyxins, and high-dose extended-infusion meropenem when treating resistant gram-negative infections 1
  • TDM-guided aminoglycoside therapy reduces nephrotoxicity (2.8% vs 13.4%) and mortality compared to non-TDM approaches 1
  • Polymyxin dosing is highly variable; TDM optimizes achievement of therapeutic targets, particularly in patients with creatinine clearance ≥80 mL/min 1

Multidisciplinary Team Approach

• Implementation of a multidisciplinary management team (intensivist, infectious disease physician, clinical pharmacologist, microbiologist) significantly reduces microbiological failure (10.3% vs 29.9%) and new MDRO colonization (8.3% vs 36.6%) 2
• Infectious disease consultation improves time to optimal therapy when combined with rapid diagnostic testing 3

Rapid Diagnostics

• Utilize rapid diagnostic tests to identify organisms and resistance mechanisms within hours of gram stain 3
• This accelerates time to optimal therapy from 47 hours to approximately 25 hours 3

Common Pitfalls to Avoid

• Do not use carbapenem-based combination therapy for CRE unless meropenem MIC is ≤8 mg/L and newer agents are unavailable 1
• Avoid empiric carbapenem overuse: In settings with multidisciplinary teams, empiric carbapenem use can be safely reduced (40.3% vs 62.7%) while maintaining appropriate coverage 2
• Do not use monotherapy with older agents (polymyxins, aminoglycosides, tigecycline, fosfomycin) for severe pan-resistant infections; always use combination therapy 1
• Recognize that newer antibiotics have predominant activity against KPC-producing organisms but variable activity against MBL and OXA producers 4