Diagnosis of bacteremia in febrile neutropenic episodes in children with cancer: microbiologic and molecular approach.

BACKGROUND: Bacterial isolation using conventional microbiologic techniques rarely surpasses 25% in children with clinical and laboratory findings indicative of an invasive bacterial infection. The aim of this study was to determine the role of real-time polymerase chain reaction (RT-PCR) from whole blood samples compared with automated blood cultures (BC) in detection of relevant microorganisms causing bacteremia in episodes of high-risk febrile neutropenia (HRFN) in children with cancer. METHODS: Children presenting with HRFN at 6 hospitals in Santiago, Chile, were invited to participate. Blood samples were obtained at admission for BC, and at admission and 24 hours for RT-PCR targeting DNA of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa causing bacteremia in children with HRFN. RESULTS: A total of 177 HRFN episodes were evaluated from May 2009 to August 2010, of which 29 (16.3%) had positive BC, 9 (5%) positive for 1 of the 3 selected bacterial species: 5 for E. coli, 3 for S. aureus, and 1 for P. aeruginosa. RT-PCR detected 39 bacteria in 36 episodes (20%): 14 E. coli, 20 S. aureus, and 5 P. aeruginosa. The sensitivity, specificity, and positive and negative predictive values of RT-PCR compared with BC were 56%, 80%, 13%, and 97%. The final clinical diagnosis was compatible with an invasive bacterial infection in 30/36 (83%) RT-PCR-positive episodes. CONCLUSIONS: In our series, RT-PCR significantly improved detection of the most relevant bacteria associated with HRFN episodes. Large number of patients and close clinical monitoring, in addition to improved RT-PCR techniques will be required to fully recommend RT-PCR-based diagnosis for the routine workup of children with cancer, fever, and neutropenia.