How to treat a urinary tract infection caused by multi-drug resistant Morganella morganii?

Treatment of Multi-Drug Resistant Morganella morganii Urinary Tract Infection

For a urinary tract infection caused by multi-drug resistant Morganella morganii, treatment with meropenem or imipenem/cilastatin/relebactam is recommended based on the susceptibility profile showing sensitivity to these agents.

Antibiotic Selection Based on Susceptibility

The urinalysis and culture results show a multi-drug resistant Morganella morganii infection with the following susceptibility pattern:

• Susceptible to: Cefoxitin, Ertapenem, Meropenem, Piperacillin/Tazobactam, Tobramycin
• Resistant to: Amoxicillin/Clavulanic Acid, Ampicillin, Ciprofloxacin, Nitrofurantoin, Tetracycline, Trimethoprim/Sulfa

First-line Treatment Options

1. Carbapenem therapy:

   • Meropenem 1g IV q8h (extended infusion over 3 hours) 1
   • Ertapenem 1g IV daily 1
   • Imipenem/cilastatin/relebactam 1.25g IV q6h 1

2. Alternative option:

   • Piperacillin/Tazobactam 4.5g IV q6h 2

Treatment Duration

• For uncomplicated UTI: 5-7 days of therapy 1, 2
• For complicated UTI (presence of fever, flank pain, or other signs of upper tract involvement): 10-14 days 2

Special Considerations

Renal Function Assessment

• Adjust dosing based on creatinine clearance:
  • For meropenem:
    • CrCl ≥50 mL/min: standard dosing
    • CrCl 26-49 mL/min: 1g q12h
    • CrCl 10-25 mL/min: 500mg q12h
  • For ertapenem:
    • CrCl ≥30 mL/min: standard dosing
    • CrCl <30 mL/min: 500mg daily 2

Monitoring Response

• Clinical improvement should be expected within 48-72 hours
• Complete the full course of antibiotics even if symptoms resolve quickly 2
• If no improvement within 72 hours, reassess diagnosis and consider imaging to rule out complications

Rationale for Treatment Selection

M. morganii is known for its intrinsic resistance to multiple antibiotics and ability to develop resistance during treatment 3, 4. Recent studies have shown increasing resistance patterns in M. morganii isolates, particularly to commonly used antibiotics for UTIs 5.

The 2022 guidelines for multidrug-resistant organisms recommend carbapenems as preferred agents for complicated UTIs caused by resistant gram-negative organisms 1. The susceptibility profile of this isolate supports this approach.

Prevention of Recurrence

• Ensure adequate hydration (2-3 liters daily)
• Frequent urination, especially after sexual intercourse
• Consider prophylactic antibiotics only for frequent recurrences 2

Pitfalls to Avoid

1. Do not treat asymptomatic bacteriuria - Treatment increases the risk of developing symptomatic infection with resistant organisms 2

2. Avoid empiric therapy without susceptibility testing - M. morganii commonly develops resistance during treatment 3

3. Do not use nitrofurantoin - M. morganii is intrinsically resistant to nitrofurantoin, which is confirmed in this susceptibility profile 4

4. Avoid fluoroquinolones - This isolate shows resistance to ciprofloxacin, and fluoroquinolone resistance is increasingly common in M. morganii 5

5. Do not rely on beta-lactam/beta-lactamase inhibitor combinations without susceptibility confirmation - M. morganii can produce AmpC β-lactamases that may not be inhibited by some beta-lactamase inhibitors 3, 4