What is the treatment for Citrobacter bacteremia?

Treatment of Citrobacter Bacteremia

For Citrobacter bacteremia, the recommended treatment is a carbapenem such as imipenem-cilastatin or meropenem, with consideration for combination therapy in severe cases or multidrug-resistant strains. 1, 2

Initial Assessment and Management

• Obtain blood cultures from both the central line (if present) and peripheral vein before starting antibiotics 3
• Assess for hemodynamic stability, source of infection, and risk factors for multidrug resistance
• Remove central venous catheters if present, especially for Citrobacter-related CLABSI 3, 4

Empiric Antibiotic Therapy

First-line options:

• Carbapenems: Imipenem-cilastatin or meropenem 1, 2
  • Imipenem-cilastatin has demonstrated consistent efficacy against Citrobacter species, including multidrug-resistant strains
  • Dosing: 500mg IV every 6 hours (adjust based on renal function)

Alternative options (based on susceptibility):

• Third-generation cephalosporins: Cefotaxime or ceftazidime 5
• Fluoroquinolones: Ciprofloxacin or levofloxacin 4, 2
• Piperacillin-tazobactam: Consider for non-resistant strains 2

Special Considerations

For multidrug-resistant Citrobacter:

• Consider combination therapy with:
  • Carbapenem plus aminoglycoside 6
  • For carbapenem-resistant strains: ceftazidime-avibactam or meropenem-vaborbactam 3

Source control:

• Identify and address the primary source of infection
• Most common sources: intra-abdominal (51%), urinary tract (20%), respiratory (11-20%) 5, 6
• Surgical drainage of abscesses or removal of infected devices is essential

Duration of Treatment

• Uncomplicated bacteremia: 10-14 days 3
• Complicated bacteremia (endovascular infection, metastatic foci): 4-6 weeks 3
• Continue treatment until:
  • Resolution of fever for at least 48-72 hours
  • Clearance of blood cultures
  • Clinical improvement

Monitoring and Follow-up

• Repeat blood cultures 48-72 hours after initiating antibiotics to document clearance 3
• Monitor for clinical response (resolution of fever, hemodynamic stability)
• Assess for complications (endocarditis, metastatic infections)
• Adjust antibiotics based on susceptibility results

Pitfalls and Caveats

• Citrobacter species, especially C. freundii, frequently develop resistance to third-generation cephalosporins during therapy due to inducible AmpC β-lactamases 2
• Prior treatment with third-generation cephalosporins is significantly associated with development of multidrug resistance 6
• Polymicrobial bacteremia is common with Citrobacter (33-46% of cases), particularly with intra-abdominal sources 5, 6
• Mortality rates are high (18-56%), especially in immunocompromised patients 5, 6

Risk Factors for Poor Outcomes

• Immunocompromised status (malignancy, transplant recipients)
• Pneumonia as source
• Septic shock
• Delayed appropriate antimicrobial therapy
• Multidrug-resistant isolates