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

Coagulase-Negative Staphylococci (Staph epidermidis) are the Most Common Organisms Isolated from Infected Central Catheters in the Femoral Vein

The most common organism isolated from infected central catheters in the femoral vein is Staphylococcus epidermidis (coagulase-negative staphylococci).

Epidemiology of Central Venous Catheter Infections

According to current guidelines, coagulase-negative staphylococci, particularly Staphylococcus epidermidis, are the predominant pathogens in central venous catheter-related bloodstream infections (CRBSIs) 1. The evidence shows a clear hierarchy of causative organisms:

1. Coagulase-negative staphylococci (60-70% of infections)
2. Staphylococcus aureus
3. Candida species
4. Gram-negative bacteria (20-25%)
5. Enterococci

Femoral Catheter-Specific Considerations

Femoral vein catheters carry a particularly high risk of infection compared to other insertion sites 1, 2. Studies specifically examining femoral catheters have confirmed that Staphylococcus epidermidis remains the most frequently isolated pathogen from these sites 3, 4.

Key points regarding femoral catheter infections:

• Femoral catheters have significantly higher rates of positive catheter tips (42% vs 6.9%) and related bacteremia (16.7% vs 1.8%) compared to non-femoral catheters 3
• The most commonly isolated organisms from femoral catheters are coagulase-negative staphylococci (primarily S. epidermidis) and Candida species 3, 2
• Femoral venous access has the highest infection risk among all central venous access sites 1, 4

Pathogenesis of Catheter Infections

The predominance of S. epidermidis in catheter infections is explained by its pathogenesis:

• Migration of skin organisms at the insertion site is the primary route of contamination 1
• S. epidermidis has the ability to form biofilms on catheter surfaces, making it particularly adept at colonizing these devices 1
• Coagulase-negative staphylococci are part of the normal skin flora, making them readily available to contaminate catheters during insertion or manipulation

Management Implications

The identification of S. epidermidis as the most common pathogen has important treatment implications:

• For suspected femoral catheter infections, empiric coverage should include agents effective against coagulase-negative staphylococci 1
• Vancomycin is often used empirically until culture results are available 1
• For confirmed S. epidermidis infections, catheter removal may be sufficient, but a 7-day course of appropriate antibiotics is generally recommended 1
• If the catheter must be retained, a longer course (10-14 days) of antibiotics plus antibiotic lock therapy is advised 1

Prevention Strategies

To reduce the risk of S. epidermidis and other infections in femoral catheters:

• Avoid femoral vein access when possible, as it carries the highest infection risk 1
• Use maximal sterile barrier precautions during insertion
• Apply chlorhexidine-based skin antisepsis before insertion and during dressing changes
• Limit catheter duration, as infection risk increases significantly after 3 days 5
• Consider antimicrobial-impregnated catheters for high-risk situations

In conclusion, while all the organisms listed in the question can cause central catheter infections, Staphylococcus epidermidis (coagulase-negative staphylococci) is clearly the most common pathogen isolated from infected central catheters, including those in the femoral vein.