Treatment of Myroides Species UTIs
Treat Myroides species UTIs with trimethoprim-sulfamethoxazole or fluoroquinolones based on antimicrobial susceptibility testing, as these organisms exhibit intrinsic multidrug resistance and require targeted therapy guided by culture results. 1, 2
Critical Clinical Context
Myroides species are emerging multidrug-resistant environmental pathogens that predominantly affect immunocompromised patients and require special consideration:
- Myroides spp. produce biofilms and demonstrate intrinsic resistance to multiple antibiotic classes, making empiric therapy unreliable 1
- Pan-resistant isolates have been documented, including strains resistant to beta-lactams, tetracyclines, sulfonamides, and macrolides 3
- These organisms are ubiquitous in water, soil, and sewage, with increasing reports of UTIs in the past two decades 1
Recommended Antibiotic Approach
First-Line Options (Based on Susceptibility Testing)
- Trimethoprim-sulfamethoxazole has demonstrated clinical success in documented Myroides UTI cases 1
- Fluoroquinolones (ciprofloxacin or levofloxacin) have proven effective in multiple case reports, though susceptibility is variable 2, 3
Treatment Duration
- 7-14 days of therapy is recommended, following complicated UTI guidelines since Myroides infections typically occur in immunocompromised hosts 4
- Male patients require 14 days of treatment to exclude prostatitis 4
Essential Management Steps
Mandatory Culture and Susceptibility Testing
- Always obtain urine culture before initiating therapy for suspected Myroides infection 4
- Antimicrobial susceptibility testing is absolutely critical due to unpredictable resistance patterns and variable susceptibility to aminoglycosides, fluoroquinolones, and trimethoprim-sulfamethoxazole 2, 3
- Do not rely on empiric therapy alone—adjust antibiotics based on final susceptibility results 1
Alternative Agents (If Susceptible)
- Piperacillin-tazobactam may be effective in susceptible isolates 3
- Carbapenems have shown variable activity 3
- Aminoglycosides demonstrate inconsistent susceptibility and should only be used if testing confirms activity 2
Critical Pitfalls to Avoid
- Do not use standard empiric UTI regimens (nitrofurantoin, fosfomycin, or cephalosporins) as Myroides exhibits intrinsic resistance to many common agents 1
- Recognize treatment failure early—if symptoms persist after 48-72 hours on empiric therapy, suspect atypical or resistant pathogens like Myroides 1
- Immunocompromised patients with recurrent UTIs warrant broader microbiological investigation beyond typical uropathogens 1
- Environmental exposure history (water sources, sewage contact) may provide diagnostic clues 1