In general, the diagnostic approach to catheter-related blood stream infection (CRBSI) consists of clinical evaluation and microbiologic confirmation with peripheral blood and catheter cultures. Catheter-related bloodstream infection (CRBSI) should be suspected when bloodstream infection occurs in the setting of a central venous catheter with no other apparent source.
Fever is the most sensitive clinical manifestation. Other clinical manifestations include hemodynamic instability, altered mental status, catheter dysfunction, and clinical signs of sepsis that start abruptly after catheter infusion.
Cultures of blood and catheters should be pursued in the setting of clinical suspicion for CRBSI when the local microbiology laboratory has appropriate resources for such testing. Blood cultures positive for S. aureus, coagulase-negative staphylococci or Candida species in the absence of other identifiable sources of infection should increase the suspicion for CRBSI.
Paired blood samples drawn from the catheter and a peripheral vein should be obtained for culture prior to initiation of antibiotic therapy. Microbiologic confirmation of CRBSI may be made based blood culture data meeting one of the following criteria．
•Culture of the same organism from both the catheter tip and at least one percutaneous blood culture.
•Culture of the same organism from at least two blood samples (one from a catheter hub and the other from a peripheral vein or second lumen) meeting criteria for quantitative blood cultures or differential time to positivity.
Most laboratories do not perform quantitative blood cultures, but many laboratories are able to determine differential time to positivity (DTP). DTP refers to growth detected from the catheter hub sample at least two hours before growth detected from the peripheral vein sample.
Catheter cultures should be performed when a catheter is removed for suspected catheter-related bloodstream infection; there is no role for routine catheter cultures in the absence of clinical suspicion for infection. Catheter colonization is established by the following quantitative definitions．
•Semiquantitative broth culture growth of >15 colony forming units (cfu) from a 5-cm segment of the catheter tip by roll-plate culture. Short term catheter tips should be evaluated using this technique.
•Quantitative broth culture of >10(2) cfu from a catheter by sonication by broth culture.