What is the recommended treatment for Raoultella species infections?

Treatment of Raoultella Species Infections

For Raoultella species infections, treatment should be guided by antimicrobial susceptibility testing, with carbapenems (imipenem or meropenem) being the most reliable first-line options due to their high susceptibility rates of >98%.

Antimicrobial Susceptibility Profile

Raoultella species are gram-negative, rod-shaped bacteria belonging to the Enterobacteriaceae family. According to recent studies, Raoultella strains demonstrate the following susceptibility patterns 1:

• Imipenem: 99.0% susceptible
• Meropenem: 98.1% susceptible
• Gentamicin: 93.3% susceptible
• Ciprofloxacin: 92.4% susceptible

Treatment Algorithm Based on Infection Severity

Severe Infections (Sepsis, Bacteremia, Deep-seated Infections)

1. First-line therapy:

   • Carbapenem (imipenem or meropenem) monotherapy if susceptible
   • For carbapenem-resistant Raoultella (CRR):
     • Use combination therapy with two in vitro active drugs 2
     • Consider ceftazidime-avibactam if available and susceptible 2

2. Alternative options:

   • Piperacillin-tazobactam if susceptible
   • Fluoroquinolones (ciprofloxacin or levofloxacin) if susceptible
   • Aminoglycosides (gentamicin) if susceptible

Non-severe Infections (UTI, Mild Pneumonia)

1. First-line therapy:

   • Monotherapy with the narrowest-spectrum in vitro active agent 2
   • Consider cephalosporins, fluoroquinolones, or aminoglycosides based on susceptibility

2. Duration of therapy:

   • UTI: 7-14 days
   • Pneumonia: 7-14 days
   • Bacteremia: 14 days
   • Deep-seated infections (liver abscess): 2-4 weeks

Special Considerations

Intra-abdominal Infections (e.g., Liver Abscess)

For intra-abdominal infections caused by Raoultella species:

1. Antimicrobial therapy:

   • Combination of surgical/percutaneous drainage plus antibiotics 3
   • For community-acquired infections: ertapenem, piperacillin-tazobactam, or ceftriaxone plus metronidazole 2
   • For healthcare-associated infections: carbapenem or piperacillin-tazobactam 2

2. Source control:

   • Drainage of abscesses is crucial for successful treatment

Catheter-Related Bloodstream Infections

For Raoultella species causing catheter-related infections:

1. Catheter management:

   • Remove short-term catheters 2
   • For long-term catheters, removal is generally recommended, especially with persistent bacteremia 2

2. Antimicrobial therapy:

   • 7-14 days of appropriate antibiotics based on susceptibility testing 2

Resistance Mechanisms and Monitoring

Approximately 12.4% of Raoultella strains produce extended-spectrum beta-lactamases (ESBLs), and some rare strains may produce both ESBLs and metallo-beta-lactamases (MBLs) 1. For ESBL-producing strains:

1. Treatment options:

   • Carbapenems remain the most reliable option
   • Avoid cephalosporins and penicillins without beta-lactamase inhibitors

2. For carbapenem-resistant strains:

   • Use combination therapy with two in vitro active agents 2
   • Consider newer agents like ceftazidime-avibactam if available and susceptible

Clinical Outcomes

Clinical outcomes for Raoultella infections are generally favorable with appropriate antimicrobial therapy. In a study of Raoultella planticola pneumonia, all isolates were susceptible to cephalosporins, carbapenems, fluoroquinolones, aminoglycosides, and beta-lactams/beta-lactamase inhibitors, with favorable outcomes after empirical antibiotic therapy 4.

Common Pitfalls

1. Misidentification: Raoultella species may be misidentified as Klebsiella species by some automated systems
2. Underestimating resistance: Always perform susceptibility testing as resistance patterns can vary
3. Inadequate source control: Particularly for abscesses, drainage is essential alongside antimicrobial therapy
4. Overlooking emerging resistance: Monitor for development of resistance during therapy, especially with prolonged treatment courses

Remember that while Raoultella infections are relatively rare, they can cause serious infections, particularly in immunocompromised patients or those with underlying conditions such as malignancies or chronic diseases 4, 5.