Background: Catheter-related bloodstream infection (CRBSI) is one of the leading types of infection, with a significant morbidity and mortality rate. We evaluated the differential time to positivity (DTP) and semi-quantitative culture of catheter segments (SQCC) as a method for diagnosing CRBSI. 

Methods: From January 2010 to August 2011, 155 positive paired blood cultures which had the same organism isolated from blood cultures drawn simultaneously through the central venous catheter (CVC) and the peripheral vein were included. Positive DTP represents a DTP of least 120 min earlier for the time to detection of CVC draw than that of a peripheral vein draw. We evaluated the clinical utility of DTP and SQCC for diagnosing CRBSIs, which were further divided into two groups: confirmed (either by DTP or SQCC) and non-confirmed CRBSIs (neither DTP nor SQCC positive). 

Results: Sixty-five percent (100/155) of episodes were confirmed to CRBSIs. In CRBSIs, Gram-positive cocci accounted for 61% of cases, non-fermenting Gram-negative bacilli represented 10%, Enterobacteriaceae for 10%, yeasts for 15%, and others for 4%. Among the confirmed CRBSI cases, 22 were both positive with DTP and SQCC, 30 cases were positive with DTP only, 12 cases were positive with SQCC only, and 36 cases which did not undergo SQCC analysis were DTP positive. The sensitivities of the DTP and SQCC techniques were 88.0% (88/100) and 53.1% (34/64), respectively. 

Conclusion: The differential time to positivity was more sensitive than the semi-quantitative culture of catheter segments for the diagnosis of CRBSIs. DTP is useful for diagnosing CRBSIs without removal of the catheter. (Korean J Clin Microbiol 2012;15:125- 130)