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Introduction: Our objective was to determine whether there is a cut-off in the needleless connectors’ (NCs) cultures that when combined with skin cultures it was as efficient as conventional superficial cultures to rule-out catheter colonization (CC) and catheter-related bloodstream infection (CRBSI). Methods: During 10 months, we collected samples and then we analyzed the validity values of skin+NCs cultures for CC and CRBSI considering the best cut-off showing at least >90% of specificity to have a high negative predictive value using a ROC curve. Results: We collected a total of 167 catheters. The optimal cut-off of NCs culture was 1000cfu/NC. The validity values for CC and CRBSI combining skin cultures and NCs cultures using the selected cut-off were, respectively: S, 42.9%/16.7%; SP, 83.6%/75.8%; PPV, 27.3%/2.5%; and NPV, 91.0%/96.0%. Conclusions: The combination of skin cultures and quantitative NCs cultures could be used for ruling-out CC and CRBSI.(AU)

Introducción: Nuestro objetivo fue determinar si existe un punto de corte en los cultivos de conectores sin aguja (NC) que, cuando se combina con cultivos de piel, sea tan eficiente como los cultivos superficiales convencionales para descartar colonización de catéter (CC) y bacteriemia relacionada con el catéter (BRC). Métodos: Durante 10 meses se coleccionaron muestras, y después se analizaron los valores de validez de los cultivos de piel + NC para CC y BRC considerando el mejor punto de corte aquel que mostrara al menos >90% de especificidad para tener un alto valor predictivo negativo usando una curva ROC. Resultados: Se estudiaron un total de 167 catéteres. El punto de corte óptimo del cultivo de NC fue de 1.000ufc/NC. Los valores de validez para CC y BRC combinando cultivos de piel y cultivos de NC utilizando el punto de corte seleccionado fueron, respectivamente: S: 42,9/16,7%; ES: 83,6/75,8%; VPP: 27,3/2,5% y VPN: 91,0/96,0%. Conclusiones: La combinación de cultivos de piel y cultivos cuantitativos de NC podría usarse para descartar CC y BRC.(AU)

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INTRODUCTION: Our objective was to determine whether there is a cut-off in the needleless connectors' (NCs) cultures that when combined with skin cultures it was as efficient as conventional superficial cultures to rule-out catheter colonization (CC) and catheter-related bloodstream infection (CRBSI). METHODS: During 10 months, we collected samples and then we analyzed the validity values of skin+NCs cultures for CC and CRBSI considering the best cut-off showing at least >90% of specificity to have a high negative predictive value using a ROC curve. RESULTS: We collected a total of 167 catheters. The optimal cut-off of NCs culture was 1000cfu/NC. The validity values for CC and CRBSI combining skin cultures and NCs cultures using the selected cut-off were, respectively: S, 42.9%/16.7%; SP, 83.6%/75.8%; PPV, 27.3%/2.5%; and NPV, 91.0%/96.0%. CONCLUSIONS: The combination of skin cultures and quantitative NCs cultures could be used for ruling-out CC and CRBSI.

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This revision describes in detail the different diagnostic techniques of catheter-related infection, both in terms of catheter removal and preservation. Culture techniques based on catheter withdrawal are classified depending on the detection of extraluminal and/or intraluminal colonization, and new methodologies are described. In general, the most important recommendations are: (a) do not send for culture catheter tips without suspicion of infection, (b) Maki's technique is the standard for detecting extraluminal colonization, (c) take 2 pairs of peripheral blood cultures before starting antibiotic treatment, (d) use skin and connections/connectors cultures for the conservative diagnosis due to their high negative predictive value (Gram and culture), and (e) take differential quantitative blood cultures though all catheter lumens and through a peripheral vein.

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We compared in an vitro model the yields of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and conventional culture (CC) for the detection of catheter colonization with superficial catheter samples (SS). We used blood culture bottles (BCB) with an inserted cannula and incubated at 37 °C. The BCB were manipulated with different contaminations and when a BCB turned positive, SS were obtained to perform both techniques. To compare both techniques we analyzed the mean time to colonization (MTC) and the mean time to a result (MTR). The MTC (SD, days) by CC and MALDI-TOF was as follows: hub, 0.59 (0.79) versus 1.07 (1.39), P=0.06; surface: 0.62 (0.67) versus 0.82 (0.81), P<0.001. The MTR (SD, days) of CC and MALDI-TOF was as follows: hub: 1.58 (0.79) versus 2.25 (1.48), P=0.04; surface: 1.62 (0.67) versus 1.95 (0.80), P<0.001. In general, the use of MALDI-TOF performed directly with SS was no better than CC and did not anticipate colonization results.

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We performed a prospective study in patients with tunneled catheters to assess the validity of Gram stain and superficial culture for anticipating catheter exit-site infection and hemodialysis catheter-related bloodstream infection. The sensitivity and negative predictive value were high, and we succeeded in identifying a subpopulation at low risk of infection.

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