What is the recommended treatment for Raoultella ornithinolytica infections?

Treatment of Raoultella ornithinolytica Infections

Raoultella ornithinolytica infections should be treated with a carbapenem-based regimen (such as meropenem) or a beta-lactam/beta-lactamase inhibitor combination, with therapy guided by antimicrobial susceptibility testing.

Pathogen Overview

Raoultella ornithinolytica is a gram-negative bacillus belonging to the Enterobacteriaceae family that is emerging as a significant human pathogen. Once considered primarily environmental, it is increasingly recognized as causing serious infections in both immunocompromised and immunocompetent individuals 1.

Clinical Presentations

R. ornithinolytica can cause various infections including:

• Urinary tract infections (36% of cases)
• Respiratory infections including pneumonia (24%)
• Gastrointestinal infections (14%)
• Wound and skin infections (13%)
• Bacteremia (5%)
• Less common: osteomyelitis, meningitis, cerebral abscess, mediastinitis, pericarditis 1

Antimicrobial Susceptibility

R. ornithinolytica demonstrates concerning resistance patterns:

• 4% resistance to ceftriaxone
• 6% resistance to quinolones
• 13% resistance to co-trimoxazole 1
• Some isolates show multidrug resistance 2
• Generally susceptible to carbapenems and piperacillin/tazobactam 3

Treatment Recommendations

First-line Treatment

1. For severe infections:

   • Meropenem 2g IV q8h (extended infusion over 3 hours) 4
   • Alternative: Imipenem/cilastatin 500mg IV q6h 4

2. For non-severe infections:

   • Piperacillin/tazobactam 4.5g IV q6h 3
   • Ceftriaxone 2g IV daily (if susceptible) 4

Alternative Regimens

• For patients with penicillin allergies: Ceftazidime-avibactam 2.5g IV q8h 4
• For urinary tract infections (if susceptible): Trimethoprim-sulfamethoxazole 160/800mg PO twice daily for 10-14 days 5

Special Considerations

For Complicated Intra-abdominal Infections

• Meropenem 2g IV q8h or imipenem/cilastatin 500mg IV q6h 4
• Alternative: Piperacillin/tazobactam with extended infusion 4

For Bloodstream Infections

• Carbapenem-based therapy is recommended (meropenem or imipenem) 4
• Duration: 10-14 days 4

For Urinary Tract Infections

• If susceptible, oral step-down therapy with amoxicillin-clavulanate 875mg PO three times daily can be considered 5
• Duration: 10-14 days for complicated UTIs 5

Treatment Duration

• Bloodstream infections: 10-14 days
• Pneumonia: at least 7 days
• Complicated intra-abdominal infections: 7-14 days
• Complicated urinary tract infections: 10-14 days 4

Monitoring and Follow-up

• Clinical improvement should be seen within 48-72 hours
• Follow-up cultures may be necessary if symptoms persist
• Monitor for development of resistance during therapy

Important Considerations

• Infectious disease consultation is highly recommended for management of infections caused by this multidrug-resistant organism 4
• Antimicrobial susceptibility testing is crucial to guide definitive therapy 4
• Prolonged infusion of beta-lactams is recommended for pathogens with high MICs 4
• R. ornithinolytica should never be considered merely a contaminant when isolated from clinical specimens 1

Pitfalls to Avoid

• Do not delay appropriate broad-spectrum antibiotic therapy while awaiting culture results, as mortality rate related to R. ornithinolytica infection can reach 5% 1
• Avoid fluoroquinolone monotherapy due to increasing resistance rates 1
• Do not underestimate the pathogenicity of R. ornithinolytica, especially in patients with underlying malignancies 3

Remember that R. ornithinolytica is an emerging hospital-acquired infection often associated with invasive procedures, but community-acquired cases have also been reported 6.