What antibiotic is effective against Stenotrophomonas maltophilia?

Treatment of Stenotrophomonas maltophilia Infections

High-dose trimethoprim-sulfamethoxazole (TMP-SMX) at 15-20 mg/kg/day of the trimethoprim component is the first-line treatment for Stenotrophomonas maltophilia infections. 1

First-Line Treatment

• TMP-SMX (first choice):
  • Dosing: 15-20 mg/kg/day of trimethoprim component
  • Duration: 7-14 days, based on clinical response
  • Administration: Can be given orally or intravenously depending on infection severity
  • Evidence: Recommended by the American College of Clinical Pharmacy and supported by clinical outcomes 1

Alternative Options for TMP-SMX Intolerant or Resistant Cases

1. Minocycline:

   • Demonstrated comparable efficacy to TMP-SMX in clinical studies 1
   • Particularly useful in patients with recent acute kidney injury
   • High susceptibility rate (95%) even against TMP-SMX resistant strains 2

2. Tigecycline:

   • Appropriate alternative with good activity against S. maltophilia 1
   • Shows consistent activity against TMP-SMX resistant strains 2
   • Clinical studies show comparable outcomes to TMP-SMX with 68.4% clinical improvement at 14 days 3

3. Fluoroquinolones:

   • Levofloxacin has emerged as a reasonable alternative to TMP-SMX 4
   • Recent data suggests levofloxacin may have similar or potentially better outcomes compared to TMP-SMX, especially for respiratory infections 4
   • Moxifloxacin is another option with good in vitro activity 2

Combination Therapy for Severe Infections

The Infectious Diseases Society of America recommends considering combination therapy for severe S. maltophilia infections 1, 5. Potentially effective combinations include:

• TMP-SMX plus moxifloxacin (shows synergism against strains with low moxifloxacin MICs) 2
• Moxifloxacin plus minocycline 2
• Moxifloxacin plus tigecycline 2

Newer Treatment Options

For multidrug-resistant strains, newer options with promising clinical data include:

• Cefiderocol (FDC) 5
• Ceftazidime-avibactam plus aztreonam (CZA-ATM) 5

Antimicrobials with Poor Activity Against S. maltophilia

The following should be avoided as monotherapy:

• Ceftazidime (only 20% susceptibility) 2
• Polymyxin E/Colistin (22.5% susceptibility) 2
• Chloramphenicol (37.5% susceptibility) 2

Treatment Monitoring and Adjustment

• Evaluate clinical response daily
• If no improvement after 7 days, consider:
  • Repeating microbiological studies
  • Changing antimicrobial regimen
  • Adding a second agent for synergistic effect 1

Important Considerations

• In vitro susceptibility may not always predict clinical efficacy for S. maltophilia infections 1
• Base antibiotic selection on local susceptibility patterns and specific isolate testing when available
• For immunocompromised patients, aggressive determination of infection etiology through aspiration/biopsy is recommended to guide therapy 1

The treatment of S. maltophilia infections remains challenging due to intrinsic multidrug resistance. While TMP-SMX remains the gold standard, minocycline and tigecycline offer effective alternatives with good clinical outcomes, particularly for TMP-SMX resistant strains.