Sepsis is the leading cause of morbidity and mortality in critically ill patients worldwide [1]. Rapid and accurate microbiological data, especially from blood culture, prevent inadequate antimicrobial treatment, which has been reported as the most important independent predictor of hospital mortality in intensive care unit (ICU) patients [2, 3]. Unfortunately, blood culture provides high speci-


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Claudio Ronco, MD

Department of Nephrology, Dialysis and Transplantation St Bortolo Hospital, Viale Ridolfi 31 IT-36100 Vicenza (Italy)

Tel. +39 0444 753 869, Fax +39 0444 753 949, E-Mail [email protected]

ficity but low sensitivity. It has long been known that more than two thirds of clinically suspected sepsis patients have negative blood cultures [4, 5]. Consequently it is necessary to identify the infectious pathogens as soon as the clinical picture of sepsis is seen, especially when conventional blood culture has been negative.

Little is known about plasma circulating DNA, but baseline low levels are present in healthy subjects [6, 7]. DNA probably enters the circulation following cell death (necrosis or apoptosis). Furthermore, the clearance mechanism of circulating DNA is poorly understood, although the liver and the kidneys play a major role for its removal [7]. Plasma DNA also has a bacterial origin in septic patients. Molecular methods have been developed for the detection and identification of bacterial DNA, which exploits the characteristics of the bacterial 16S rRNA gene: this gene consists of highly conserved regions and mixes together highly variable regions, which allow phylogenet-ic analysis.

The present study aimed to: (1) make a comparison between standard blood culture and 16S rRNA gene sequence analysis in order to validate the usefulness of molecular methods for biological diagnosis in septic patients, and (2) determine whether bacterial DNA is adsorbed within the hemofilter, and if it can pass through the hemofilter and be present in ultrafiltrate (UF) of patients with severe sepsis undergoing continuous renal replacement therapy (CRRT).

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