What is the recommended treatment for a patient with Weissella cibaria isolated in one set of blood cultures?

Management of Weissella cibaria in Blood Cultures

For a patient with Weissella cibaria isolated in one set of blood cultures, catheter removal is recommended along with appropriate antimicrobial therapy based on susceptibility testing, as this organism is inherently resistant to vancomycin.

Background and Significance

Weissella cibaria is a gram-positive coccobacillus that belongs to the Lactobacillaceae family. It is often misidentified by traditional and commercial phenotypic identification methods as Lactobacillus or Lactobacillus-like organisms 1. Though rarely reported as a cause of human infections, Weissella species have been implicated in bacteremia, particularly in immunocompromised hosts 1, 2.

Diagnostic Considerations

• Blood cultures showing gram-positive coccobacilli that are vancomycin-resistant should raise suspicion for Weissella species 2
• Accurate identification often requires 16S rRNA gene sequencing as commercial automated systems frequently misidentify these organisms as Lactobacillus or Leuconostoc species 3, 2
• Additional blood cultures should be obtained to determine if the organism represents true bacteremia versus contamination 4
• If a catheterized patient has a single positive blood culture, additional cultures from both the catheter and peripheral vein should be performed before initiating antimicrobial therapy 4

Risk Factors for True Weissella Bacteremia

• Presence of central venous catheters 3
• Immunocompromised status, particularly malignancy 3, 2
• Recent surgery within the previous 3 months 3
• Total parenteral nutrition 5
• Alterations of gut flora from surgery or chemotherapy 1

Management Recommendations

Catheter Management

• For a single positive blood culture with Weissella cibaria, the catheter should generally be removed after ruling out blood culture contamination 4
• Short-term catheters should be removed from patients with catheter-related bloodstream infections (CRBSI) due to gram-positive bacilli 4
• If the catheter is a long-term device and removal poses significant challenges, consider catheter exchange over a guidewire if the patient has no signs of exit site or tunnel infection 4

Antimicrobial Therapy

• Weissella species are inherently resistant to vancomycin, making empiric vancomycin therapy ineffective 1, 2

• Based on susceptibility data, the following antibiotics have shown good activity against Weissella species:

  • Daptomycin (MIC ≤0.12 mg/L) 3, 2
  • Linezolid (MIC ≤4 mg/L) 3
  • Tigecycline (MIC ≤0.12 mg/L) 3
  • Moxifloxacin 3

• Duration of therapy:

  • For uncomplicated CRBSI: 10-14 days of appropriate antimicrobial therapy 4
  • For complicated infections (endocarditis, septic thrombosis): 4-6 weeks 4

Monitoring Response

• Obtain follow-up blood cultures 72 hours after initiating appropriate antimicrobial therapy 4
• If blood cultures remain positive after 72 hours of appropriate therapy, catheter removal is mandatory if not already performed 4

Special Considerations

• Mortality has been directly attributed to Weissella bacteremia in immunocompromised patients 3
• Concomitant polymicrobial bacteremia is common (reported in 50% of cases), suggesting possible gastrointestinal translocation 3
• Weissella cibaria exhibits high MICs to trimethoprim-sulfamethoxazole and ceftazidime (≥128 mg/L), making these antibiotics ineffective 3

Common Pitfalls

• Misidentification as Lactobacillus or other gram-positive organisms by routine laboratory methods 1, 2
• Inappropriate empiric treatment with vancomycin due to the organism's intrinsic resistance 2, 5
• Dismissing the organism as a contaminant when isolated from multiple blood cultures in an at-risk patient 1
• Failure to remove an infected catheter, leading to persistent bacteremia 2

Early identification, appropriate antimicrobial selection based on susceptibility testing, and consideration of catheter removal are essential for successful management of Weissella cibaria bacteremia.