Molecular diagnosis of bacteriemia in patients with neutropenic febrile oncohematologic.

Abstract

9033 Background: The rapid microbiologic diagnosis in the course of fever of unknown origin plays an important role for the appropriate treatment in neutropenic patients. Blood culture helps identify bacterial and fungal bacteriemia. However, its efficacy can be limited due to its low sensitivity when the patient is receiving antibiotics and to the long time required to identify the pathogen (24-72 hours). Septifast (Roche Molecular Systems) is a new molecular technique which detects in 6 hours the 25 most important bacterial and fungal species reported to cause bloodstream infections. The aim of the study was to compare Septifast with conventional blood cultures in blood samples from neutropenic febrile patients. Methods: Forty-five blood samples from 19 patients were prospectively tested. All of them presented fever with neutrophil count <0.5x109/L. The patients (pts) were receiving antibiotic therapy (piperaciline-tazobactam/imipenem (19pts), vancomicine (7pts), amikacine (3pts), aciclovir (2pts) and antifungal therapy (9pts). For each sample, two blood culture vials for aerobic/anaerobic cultures and an EDTA whole-blood samples for Septifast were drawn. Results: Thirty-two percent of patients presented a positive result. Eight of the 45 (17.7%) blood samples studied were positive by PCR assay (S.aureus: 2; P.aeruginosa: 3; E.coli: 1; Coagulase-negative Staphylococci: 2). Two blood samples were positive for P.aeruginosa and Coagulase-negative Staphylococci by both Septifastâ and blood culture. The entire negative PCR test results correlated with negative blood culture samples. The negative predictive value was 100% with a sensitivity of 100% and a specificity of 86% (Table). Conclusions: Septifast is an easy and sensitive method for detecting pathogens in severely immunocompromised patients, allowing results in a shorter time and with higher sensitivity than conventional blood cultures. Comparision results from Septifast test and conventional blood culture system. Blood culture Results Positive samples (%) Negative samples (%) Total Septifast Positive samples (%) 2 (4.4) 6 (13.3) 8 (17.7) Negative samples (%) 0 (0) 37 (82.2) 37 (82.2) Total (%) 2 (4.4) 43 (95.5) 45 (100)