What is the most common organism isolated from infected central catheters, specifically those in the femoral vein?

Most Common Organism Isolated from Infected Central Catheter in Femoral Vein

Coagulase-negative staphylococci, particularly Staphylococcus epidermidis, are the most common organisms isolated from infected central venous catheters, including those placed in the femoral vein (Answer C). 1

Epidemiology of Central Venous Catheter Infections

Central venous catheter-related bloodstream infections (CRBSIs) are primarily caused by:

1. Coagulase-negative staphylococci (60-70% of cases) - particularly S. epidermidis 1
2. Candida species (5-13%)
3. Staphylococcus aureus
4. Enterococci
5. Gram-negative bacteria (20-25%) including Escherichia coli, Pseudomonas aeruginosa, and Klebsiella species

The 2017 ACR Appropriateness Criteria specifically states that "Coagulase-negative staphylococci are the most common pathogens in CRBSIs, followed by Candida, S. aureus, enterococcus, pseudomonas, and acinetobacter" 1.

Femoral Vein Catheter-Specific Considerations

Femoral vein catheters carry a higher risk of infection compared to other sites:

• Femoral catheters have shown significantly higher rates of positive catheter tips (42% vs 6.9%) and related bacteremia (16.7% vs 1.8%) compared to non-femoral catheters 2
• The femoral site has the highest infection risk among all central venous access sites, followed by centrally inserted catheters, peripherally inserted central catheters, and totally implantable devices 1
• Studies specifically examining femoral catheter infections have confirmed that S. epidermidis is the predominant organism 3, 4

Pathogenesis of Catheter-Related Infections

The primary routes of contamination for central venous catheters are:

1. Migration of skin organisms at the insertion site (65% of cases)
2. Hub contamination (30%)
3. Hematogenous seeding from another infection site
4. Contaminated infusate (rare)

Femoral catheters are particularly susceptible to infection due to:

• Proximity to the groin area with higher bacterial colonization
• Difficulty maintaining sterile dressings
• Higher moisture levels in the area
• Increased movement at the site

Risk Factors for Catheter-Related Infections

Several factors increase the risk of catheter-related infections:

• Duration of catheter in situ (>3 days)
• Emergency insertion procedures
• Multiple insertion attempts
• Femoral venous cannulation site
• Triple-lumen catheters
• Immunocompromised status
• Receiving chemotherapy or total parenteral nutrition

Clinical Implications

When managing central venous catheters, particularly those in the femoral vein:

• Monitor closely for signs of infection
• Consider early removal if infection is suspected
• Empiric antibiotic coverage should include agents effective against coagulase-negative staphylococci
• For femoral catheters specifically, implement more frequent site care and dressing changes
• Consider alternative access sites when possible, as the subclavian vein has the lowest infection risk, followed by jugular, basilic, and femoral veins 4

Understanding that S. epidermidis is the most common pathogen in infected central catheters helps guide empiric antimicrobial therapy and infection prevention strategies.