What antibiotics (abx) are used to treat Proteus infections in the blood?

Treatment of Proteus Bacteremia

For bloodstream infections caused by Proteus species, piperacillin-tazobactam is the recommended first-line antibiotic treatment, with carbapenems (particularly meropenem) being excellent alternatives for more resistant strains. 1, 2

First-Line Treatment Options

• Piperacillin-tazobactam 3.375g IV every 6 hours or 4.5g every 8 hours is highly effective against Proteus bloodstream infections, with susceptibility rates of approximately 95.9% 2
• Carbapenems are excellent alternatives:
  • Meropenem 1g IV every 8 hours (preferred carbapenem due to higher activity against gram-negative bacteria) 3
  • Ertapenem 1g IV every 24 hours (for non-Pseudomonas coverage) 4
  • Imipenem-cilastatin 500mg IV every 6 hours (note: lower susceptibility rates for Proteus mirabilis compared to other carbapenems) 4, 5

For Multidrug-Resistant Proteus (CRE)

For carbapenem-resistant Enterobacterales (CRE) including resistant Proteus:

• Ceftazidime-avibactam 2.5g IV every 8 hours is recommended for bloodstream infections caused by CRE 1
• Meropenem-vaborbactam 4g IV every 8 hours is an alternative option 1
• Imipenem-cilastatin-relebactam 1.25g IV every 6 hours can be considered 1
• For highly resistant strains, polymyxin-based combinations may be necessary:
  • Colistin 5mg CBA/kg IV loading dose, then 2.5mg CBA (1.5 CrCl + 30) IV every 12 hours plus either:
    • Tigecycline 100mg IV loading dose, then 50mg IV every 12 hours, or
    • Meropenem 1g IV every 8 hours by extended infusion 1

Special Considerations

• Aminoglycosides are effective against many Proteus strains:

  • Amikacin 15mg/kg IV daily (86.7% susceptibility reported) 2
  • Gentamicin 5-7mg/kg IV daily can be considered, particularly for urinary source bacteremia 1

• Extended infusion of beta-lactams is recommended for pathogens with high MICs to optimize pharmacodynamics 1

• Infectious disease consultation is highly recommended for management of bloodstream infections caused by multidrug-resistant organisms 1

Duration of Therapy

• For uncomplicated Proteus bacteremia: 7-14 days of therapy is recommended 1
• Duration should be individualized based on:
  • Source control (particularly important for urinary source, which is common with Proteus) 2
  • Clinical response to therapy 1
  • Presence of metastatic foci of infection

Source Control

• Since Proteus bacteremia is frequently secondary to urinary tract infections, source control is essential 2
• Remove or replace urinary catheters if present 2
• Drain any abscesses or collections that may be the source of bacteremia 1

Monitoring

• Follow blood cultures to document clearance of bacteremia 1
• Monitor renal function, particularly when using aminoglycosides or colistin-based regimens 1
• Assess for clinical improvement including resolution of fever and hemodynamic stability 1

Antibiotic Susceptibility Considerations

• Proteus mirabilis has intrinsically reduced susceptibility to imipenem compared to other carbapenems 5
• Fluoroquinolones (ciprofloxacin, levofloxacin) are active against many Proteus strains but resistance is increasingly common 6, 7
• Proteus species are naturally resistant to colistin, which limits options for extremely drug-resistant strains 5

Remember that empiric therapy should be adjusted based on culture and susceptibility results once available to ensure optimal targeted therapy 1.