What is the recommended treatment for Enterobacter (a type of gram-negative bacteria) urinary tract infection (UTI)?

Treatment of Enterobacter Urinary Tract Infections

Carbapenems are the recommended first-line treatment for Enterobacter UTIs due to their effectiveness against multidrug-resistant strains and lower risk of treatment failure compared to other antibiotics. 1

Antibiotic Selection for Enterobacter UTIs

First-line Options:

• Carbapenems: Meropenem or Imipenem are effective against Enterobacter cloacae and Enterobacter aerogenes 1
  • Dosing:
    • Meropenem: 1g IV every 8 hours
    • Imipenem: 500mg IV every 6 hours
  • Duration: 7-10 days for complicated UTIs

Second-line Options (if susceptibility confirmed):

• Fourth-generation cephalosporins (if ESBL-negative) 1
  • Cefepime: 1-2g IV every 12 hours for 7-10 days 2
  • Adjust dose based on renal function (see dosing table below)

Alternative Options for Carbapenem-resistant Enterobacter:

• Polymyxins (colistin)
• Tigecycline
• Fosfomycin (for lower UTIs only)
• Double carbapenem regimen 1
• Ceftazidime-avibactam or ceftolozane-tazobactam for multidrug-resistant strains 3

Important Considerations

Avoid These Antibiotics for Enterobacter:

• First and second-generation cephalosporins: Generally ineffective 1
• Third-generation cephalosporins: Not recommended due to increased likelihood of resistance, particularly for E. cloacae and E. aerogenes 1

Renal Dosing Adjustments for Cefepime 2:

Creatinine Clearance	Dosing Adjustment
>60 mL/min	Standard dose
30-60 mL/min	2g every 24 hours
11-29 mL/min	1g every 24 hours
<11 mL/min	500mg every 24 hours

Treatment Algorithm

1. Initial Assessment:

   • Evaluate severity (uncomplicated vs. complicated UTI)
   • Check for risk factors for multidrug resistance
   • Obtain urine culture before starting antibiotics

2. Empiric Therapy:

   • For uncomplicated UTIs with low risk of resistance:
     • Carbapenem (preferred) or fourth-generation cephalosporin if local resistance patterns support use
   • For complicated UTIs or high risk of resistance:
     • Carbapenem IV therapy

3. Targeted Therapy (after culture results):

   • Adjust based on susceptibility testing
   • De-escalate therapy if possible to prevent further resistance

Special Situations

Carbapenem-resistant Enterobacter:

• Consider combination therapy with two or more active agents
• Consult infectious disease specialist
• Options include polymyxins, tigecycline, fosfomycin, or newer agents like ceftazidime-avibactam 3

Outpatient Management:

• If susceptible, oral fluoroquinolones may be considered for step-down therapy after clinical improvement with IV antibiotics 4
• Levofloxacin has activity against Enterobacter cloacae for complicated UTIs 4

Monitoring and Follow-up

• Assess clinical response within 48-72 hours
• Consider repeat urine culture in complicated cases or treatment failure
• Monitor for development of resistance during therapy, especially with longer treatment courses

Pitfalls and Caveats

• Beware of inducible resistance: Enterobacter species can develop resistance during therapy with certain beta-lactams through induction of AmpC beta-lactamases
• Do not use third-generation cephalosporins even if initially reported as susceptible, as resistance may develop during treatment 1
• Local antibiogram data is crucial for guiding empiric therapy decisions, as resistance patterns vary geographically
• Source control is essential in complicated UTIs with structural abnormalities or obstruction

By following this evidence-based approach to treating Enterobacter UTIs, you can maximize clinical success while minimizing the risk of treatment failure and further antimicrobial resistance.