Treatment of Pseudomonas aeruginosa Urinary Tract Infection in a 75-Year-Old Male
Levofloxacin 750 mg daily for 7-10 days is the recommended treatment for this 75-year-old male with a urinary tract infection caused by Pseudomonas aeruginosa based on the susceptibility testing results. 1
Rationale for Treatment Selection
The urine culture shows a significant growth of Pseudomonas aeruginosa (>100,000 CFU/mL), indicating a true infection rather than contamination. The antimicrobial susceptibility testing reveals that this organism is susceptible to multiple antibiotics:
- Fluoroquinolones: Ciprofloxacin (MIC ≤0.25) and Levofloxacin (MIC ≤0.5)
- Beta-lactams: Ceftazidime (MIC 4), Ceftazidime/avibactam (MIC ≤4), Imipenem (MIC 2), Meropenem (MIC 2), Piperacillin/tazobactam (MIC ≤16)
- Aminoglycosides: Tobramycin (MIC ≤2)
However, the organism is resistant to Gentamicin (reported as R).
Treatment Algorithm
First-line therapy: Levofloxacin 750 mg daily for 7-10 days
- Highly bioavailable oral option
- Excellent activity against Pseudomonas aeruginosa (MIC ≤0.5)
- FDA-approved for complicated UTIs caused by Pseudomonas aeruginosa 1
Alternative options (if fluoroquinolones are contraindicated):
- Ciprofloxacin 500 mg twice daily for 7-10 days 2
- If oral therapy is not feasible, consider IV beta-lactams:
- Ceftazidime
- Piperacillin/tazobactam
- Meropenem or Imipenem
Key Considerations
Age and Renal Function
- For this 75-year-old patient, assess renal function before prescribing
- If creatinine clearance is 26-49 mL/min: maintain Levofloxacin at 500 mg once daily
- If creatinine clearance is 10-25 mL/min: reduce to 250 mg once daily 3
Treatment Duration
- For complicated UTI: 7-10 days of therapy is recommended 3
- For uncomplicated UTI: 5-7 days may be sufficient, but given the patient's age and the organism being Pseudomonas, a full 7-10 day course is warranted
Follow-up
- Clinical response should be assessed within 48-72 hours of starting treatment
- If symptoms persist beyond 72 hours, consider:
- Repeat urine culture
- Changing antibiotic based on clinical response
- Evaluating for complications or anatomical abnormalities 3
Evidence-Based Rationale
The European Urology guidelines recommend fluoroquinolones (Ciprofloxacin 500-750mg twice daily for 7 days or Levofloxacin 750mg daily for 5-7 days) as effective treatment options for UTIs 3. For Pseudomonas aeruginosa specifically, the Italian Society of Infection and Tropical Diseases recommends that when susceptibility results are available, therapy should be tailored accordingly 4.
The FDA label for Levofloxacin specifically indicates its use for complicated UTIs due to Pseudomonas aeruginosa with a 10-day treatment regimen 1. Similarly, Ciprofloxacin is also indicated for complicated UTIs caused by Pseudomonas aeruginosa 2.
Cautions and Pitfalls
Avoid aminoglycosides as monotherapy: The guidelines specifically recommend against aminoglycoside monotherapy for Pseudomonas infections 4. Additionally, this isolate is resistant to Gentamicin.
Fluoroquinolone risks: Be aware of potential adverse effects including tendinopathy, QT prolongation, and CNS effects, particularly in elderly patients.
Resistance development: Pseudomonas aeruginosa can develop resistance rapidly during treatment. Consider follow-up cultures if clinical response is inadequate 1, 2.
Underlying conditions: Evaluate for structural or functional abnormalities of the urinary tract that may complicate treatment or lead to recurrence.
By following this evidence-based approach, targeting the susceptible organism with an appropriate antibiotic at the correct dose and duration, this patient's UTI should resolve effectively while minimizing the risk of treatment failure or recurrence.