What is the best course of action for continuing antibiotic therapy and managing the suprapubic Foley catheter in a patient with a complicated UTI caused by Escherichia coli and Proteus mirabilis, who has shown improvement on meropenem and ceftriaxone?

Management of Complicated UTI with E. coli and P. mirabilis

Ceftriaxone is the optimal antibiotic choice for continuing therapy in this patient with a complicated UTI showing improvement after initial IV antibiotics. 1, 2

Assessment of Current Situation

The patient presents with:

• Altered mental status (AMS) showing some improvement
• Urine culture positive for two organisms:
  • Escherichia coli: resistant to ampicillin, ampicillin-sulbactam, cefazolin, gentamicin, piperacillin-tazobactam (intermediate), and trimethoprim-sulfamethoxazole; susceptible to cefepime, ceftriaxone, meropenem, and nitrofurantoin
  • Proteus mirabilis: resistant to cefazolin and ciprofloxacin; susceptible to ampicillin, ampicillin-sulbactam, ceftriaxone, cefepime, gentamicin, meropenem, and trimethoprim-sulfamethoxazole; resistant to nitrofurantoin
• Suprapubic Foley catheter in place
• Normal laboratory values
• Initial treatment with IV meropenem followed by ceftriaxone for 3 days

Antibiotic Recommendation

Based on the susceptibility results and clinical improvement:

1. Continue ceftriaxone 1-2g IV daily for a total of 10-14 days 1, 3

   • Both organisms are susceptible to ceftriaxone
   • Once-daily dosing is convenient and effective for UTIs caused by susceptible organisms
   • Ceftriaxone is FDA-approved for complicated UTIs caused by E. coli and P. mirabilis 1

2. Alternative option: Continue meropenem 500mg IV every 8 hours if clinical deterioration occurs on ceftriaxone 4

   • Both organisms are susceptible to meropenem
   • Reserve carbapenems for treatment failures to prevent resistance development

Catheter Management

1. Remove or replace the suprapubic Foley catheter 5
   • Catheter removal or replacement is crucial for clinical cure in catheter-associated UTIs
   • If catheter is still needed for urinary drainage, replace it once the patient has received 3-5 days of effective antibiotic therapy
   • Proteus mirabilis readily forms biofilms on catheters, making catheter exchange important for complete resolution 3

Follow-up Recommendations

1. Obtain surveillance urine culture 1 week after completing antibiotic therapy 5

   • Particularly important since the patient has a suprapubic catheter
   • If cultures remain positive, consider longer course of therapy or catheter exchange

2. Monitor mental status closely

   • Continue to assess for improvement in altered mental status
   • Complete resolution of AMS should be expected with appropriate antibiotic therapy

Special Considerations

1. Avoid nitrofurantoin for oral step-down therapy

   • While E. coli is susceptible, P. mirabilis is resistant to nitrofurantoin 3
   • Nitrofurantoin is ineffective against Proteus species due to intrinsic resistance

2. Potential oral step-down options (if clinical improvement allows):

   • Trimethoprim-sulfamethoxazole would not be appropriate as E. coli is resistant
   • Consider infectious disease consultation for oral step-down options if needed

3. Duration of therapy

   • For complicated UTI with initial altered mental status: 10-14 days total therapy 3
   • Shorter duration may be inadequate given the presence of a suprapubic catheter and previous AMS

Pitfalls to Avoid

1. Do not use fluoroquinolones despite P. mirabilis being susceptible to some, as E. coli shows resistance to ciprofloxacin

2. Do not use nitrofurantoin despite E. coli susceptibility, as P. mirabilis is resistant

3. Do not discontinue antibiotics prematurely despite clinical improvement, as catheter-associated UTIs require a full course of therapy

4. Do not continue empiric broad-spectrum therapy unnecessarily when targeted therapy with ceftriaxone is appropriate based on susceptibilities