Catheter Tip Culture Recommendations
Catheter tip cultures should be performed only when catheter-related bloodstream infection (CRBSI) is suspected, not routinely. 1
When to Perform Catheter Tip Cultures
- Catheter cultures should be done only when catheter-related bloodstream infection is suspected, not as a routine practice 1
- For suspected CRBSI, paired blood samples (from the catheter and a peripheral vein) should be obtained before starting antimicrobial therapy 1
- If there is suspicion of short-term peripheral catheter infection, the catheter should be removed, the tip cultured using a semiquantitative method, and two separate blood samples obtained for culture before starting antibiotic therapy 1
- When catheter infection is suspected and there is a catheter exit site exudate, the drainage should be swabbed for culture and Gram staining 1
Recommended Culture Methods
- Quantitative or semiquantitative cultures of catheters are recommended (A-II evidence level) 1
- Qualitative broth cultures of catheters are not recommended (E-II evidence level) 1
- For short-term catheter tip cultures, the roll plate technique is recommended for routine clinical microbiological analysis 1
- For central venous catheters (CVCs), the catheter tip should be cultured rather than the subcutaneous segment 1
- For suspected pulmonary artery catheter infection, culture the introducer tip as it provides a higher yield compared to the pulmonary artery catheter tip 1
- For cultures of anti-infective catheter tips, specific inhibitors should be used in the culture media 1
Interpretation of Results
- Growth of >15 colony-forming units (CFU) from a 5-cm segment of the catheter tip by semiquantitative (roll-plate) culture or growth of >10² CFU from a catheter by quantitative (sonication) broth culture reflects catheter colonization 1
- For long-term catheters, growth of <15 CFU/plate of the same microbe from both the insertion site culture and catheter hub culture strongly suggests that the catheter is not the source of bloodstream infection 1
- A definitive diagnosis of CRBSI requires that the same organism grow from at least one percutaneous blood culture and from a culture of the catheter tip 1
Clinical Utility and Limitations
- Recent research suggests limited clinical utility of catheter tip cultures, with one study finding that in only 2% of cases did positive catheter tip cultures lead to changes in antibiotic therapy or management 2
- Most catheter-related bloodstream infections (93%) are identified by bacteremia either before or coinciding with catheter removal 3
- The diagnostic performance of catheter tip cultures can be limited when patients have received antimicrobial therapy before catheter removal 4
- Patients with catheter tips colonized with Gram-negative microorganisms without preceding bacteremia have a high risk of subsequent Gram-negative bacteremia, particularly with arterial catheters 5
Special Considerations
- If a venous access subcutaneous port is removed for suspected CRBSI, send both the port reservoir contents and the catheter tip for culture 1
- For patients with long-term tunneled catheters, neither the sonication technique nor the roll plate method has shown superior performance in diagnosing tip colonization or CRBSI 4
- Alternative diagnostic methods that don't require catheter removal include paired quantitative blood cultures or differential time to positivity between catheter and peripheral blood cultures 1, 6
Catheter tip cultures remain an important diagnostic tool when used appropriately, but their clinical utility should be weighed against the fact that blood culture results often dictate antimicrobial therapy decisions before catheter tip culture results are available.