What is the inpatient antibiotic of choice for urine cultures positive for Pseudomonas?

Inpatient Antibiotic Treatment for Pseudomonas in Urine Cultures

For inpatient treatment of urinary tract infections with Pseudomonas aeruginosa, aminoglycoside monotherapy (such as amikacin 15 mg/kg IV once daily) is the preferred first-line treatment when susceptibility is confirmed. 1

First-Line Treatment Options

Aminoglycoside Monotherapy

• Amikacin: 15 mg/kg IV once daily 1
• Tobramycin: 5-7.5 mg/kg/day IV in divided doses 1
• Gentamicin: 5-7.5 mg/kg IV once daily 1

The 2022 guidelines from the Journal of Microbiology, Immunology and Infection specifically state that "aminoglycoside monotherapy is only indicated for urinary tract infections" when treating Pseudomonas infections 1. This recommendation is based on the high urinary concentrations achieved with aminoglycosides and their excellent activity against Pseudomonas aeruginosa.

Alternative Options Based on Susceptibility

If aminoglycosides cannot be used or the organism shows resistance, consider these alternatives:

Antipseudomonal β-lactams:

• Ceftazidime: 2 g IV every 8 hours 1, 2
• Cefepime: 2 g IV every 8-12 hours 1
• Piperacillin-tazobactam: 3.375-4.5 g IV every 6 hours 1, 3

Carbapenems:

• Meropenem: 1 g IV every 8 hours 1
• Imipenem: 500 mg IV every 6 hours 1

Fluoroquinolones (if susceptible):

• Ciprofloxacin: 400 mg IV every 8 hours 1
• Levofloxacin: 750 mg IV daily 1, 3

Special Considerations for Multidrug-Resistant Pseudomonas

For difficult-to-treat or carbapenem-resistant Pseudomonas aeruginosa (DTR-PA), consider:

1. Colistin monotherapy: 5 mg CBA/kg IV loading dose, then 2.5 mg CBA × (1.5 × CrCl + 30) IV every 12 hours 1

2. Newer agents (based on susceptibility):

   • Ceftolozane/tazobactam: 1.5-3 g IV every 8 hours 1
   • Ceftazidime/avibactam: 2.5 g IV every 8 hours 1

Treatment Duration

• Uncomplicated UTI: 5-10 days 1, 3
• Complicated UTI: 10-14 days 1, 3

Monitoring Recommendations

1. Monitor renal function closely when using aminoglycosides due to nephrotoxicity risk 4
2. Check drug levels for aminoglycosides, particularly with prolonged therapy 3
3. Monitor for ototoxicity with aminoglycosides (hearing loss, tinnitus, vertigo) 4
4. Repeat cultures if no clinical improvement after 72 hours 3

Important Caveats and Pitfalls

• Avoid aminoglycoside monotherapy for non-urinary infections due to rapid emergence of resistance 3
• Pseudomonas can rapidly develop resistance during treatment, particularly with monotherapy 3
• Consider catheter removal or replacement if present, as recommended by European Urology guidelines 3
• Avoid fluoroquinolones for empiric therapy if local resistance rate is >10%, patient has used fluoroquinolones in the last 6 months, or patient is from a urology department 3
• Adjust dosing in patients with renal impairment to prevent toxicity 4

By following these evidence-based recommendations, you can effectively treat inpatient urinary tract infections caused by Pseudomonas aeruginosa while minimizing the risk of treatment failure and antibiotic resistance.