Diagnosis of catheter-related bloodstream infection: conservative techniques.

Received 3 December 2006; accepted 4 December 2006; electronically published 6 February 2007. Reprints or correspondence: Dr. Josefina Liñares, Servicio de Microbiologı́a, Hospital de Bellvitge, 08907 L’Hospitalet de Llobregat, Barcelona, Spain (fina.linares@csub.scs.es). Clinical Infectious Diseases 2007; 44:827–9 2007 by the Infectious Diseases Society of America. All rights reserved. 1058-4838/2007/4406-0011$15.00 DOI: 10.1086/511885 Intravascular catheters have been an important technological advance for modern medicine. However, the use of intravascular catheters is associated with infection, which is a potentially life-threatening complication. Catheter-related bloodstream infection (CR-BSI) is the most serious infection associated with catheter use, and it is responsible for significant medical costs. It is estimated that ∼250,000 episodes of CR-BSI occur annually in hospitals in the United States, with an estimated attributable mortality of 12%–25%. In addition, it is well recognized that CR-BSI increases the duration of hospital stay and medical costs per patient. One-half of all nosocomial bloodstream infections in US hospitals occur in patients receiving critical care, and CR-BSI accounts for one-third of these infections [1–3]. There are 4 potential sources of catheter colonization and catheter-related infections: the skin insertion site, the catheter hub, hematogenous seeding of the catheter tip from a distant site of infection, and infusate contamination [4–6]. For decades, it has been accepted that skin colonization and the progression of microorganisms on the external surface of the catheter are the most common origins of catheter colonization and infection [4, 7, 8]. However, the relevance of the endoluminal route in the pathogenesis of CR-BSI was recognized during the mid-1980s by Sitges-Serra and colleagues [5, 6, 9]. The authors demonstrated that 70% of CRBSIs in patients with central venous catheters for parenteral nutrition were caused by hub contamination [6]. Salzman et al. [10] reported than 54% of CR-BSI episodes in neonates were preceded by or coincided with contamination of the hub. The endoluminal route is the dominant mechanism for colonization of long-term catheters, whereas recently inserted catheters are most commonly colonized by an extraluminal route [11]. Hub contamination is more often associated with bacteremia than with skin colonization [5, 6, 9–12]. Clinical findings are unreliable for establishing a diagnosis of CR-BSI, because no characteristic clinical features of CRBSI exist to distinguish this infection from infections arising from other body sites. Conventional methods of diagnosing CRBSI generally require that the catheter be removed and cultured with quantitative or semiquantitative methods. However, 180% of catheters withdrawn because of clinical suspicion of CR-BSI are removed unnecessarily, because the culture results are negative [1] In addition, the removal of a central venous catheter may be undesirable because of limited vascular access, and there could be serious complications and risks associated with reinsertion. Consequently, a number of diagnostic techniques that do not require catheter removal have been developed to diagnose CR-BSI. Conservative methods to assess catheter-tip colonization or CRBSI are an important advance and include paired quantitative blood cultures, differential time to positivity, superficial cultures of skin surrounding the portal of entry and catheter hubs, and Gram staining and the acridine orange leukocyte cytospin test [13–21]. The study by Bouza et al. [22] in this issue of Clinical Infectious Diseases prospectively compares 3 techniques (paired quantitative blood cultures, differential time to positivity, and superficial cultures) for the diagnosis of CR-BSI without catheter withdrawal in adult patients without neutropenia who had short-term central venous catheters and were admitted to intensive care units. The authors studied 204 episodes of suspected CR-BSI, and 28 of the episodes were confirmed to be CRBSI. The reference standard for the evaluation of the 3 conservative methods for diagnosis of CR-BSI was paired quanti-