Catheter Tip Culture Recommendations

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, 3
For suspected CRBSI, paired blood samples (from the catheter and a peripheral vein) should be obtained before starting antimicrobial therapy 1, 4
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 3
When catheter infection is suspected and there is a catheter exit site exudate, the drainage should be swabbed for culture and Gram staining 1, 5

Quantitative or semiquantitative cultures of catheters are recommended (A-II evidence level) 1, 3
Qualitative broth cultures of catheters are not recommended (E-II evidence level) 1, 3
For short-term catheter tip cultures, the roll plate technique is recommended for routine clinical microbiological analysis 1, 6
For central venous catheters (CVCs), the catheter tip should be cultured rather than the subcutaneous segment 1, 7
For suspected pulmonary artery catheter infection, culture the introducer tip as it provides a higher yield compared to the pulmonary artery catheter tip 1, 3
For cultures of anti-infective catheter tips, specific inhibitors should be used in the culture media 1, 6

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, 7
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, 6
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, 4

If a venous access subcutaneous port is removed for suspected CRBSI, send both the port reservoir contents and the catheter tip for culture 1, 6
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 3