Multiple Polymerase Chain Reaction for Direct Detection of Bloodstream Infection After Cardiac Surgery in a PICU

Nosocomial infections are a prevalent cause of death and complications in critically ill children. Conventional cultures are able to detect only up to 25% of bacteremia. Several studies have suggested that molecular tests could be a faster and effective tool for detection of bacterial infections. The objective of this study is to compare molecular tests for bacterial detection in whole blood samples, with routine blood culture for the diagnosis of nosocomial bloodstream infections (BSIs). DESIGN: Prospective cohort study. SETTING: A PICU of a tertiary center, reference for congenital heart diseases. PATIENTS: Children, 0–16 years, admitted to PICU between August 2016 and December 2019 after cardiac surgery were prospectively recruited. Demographic, clinical, laboratory, and microbiologic data from patient’s medical records, and laboratory and microbiologic results were collected. INTERVENTIONS: In all patients, blood culture and multiple polymerase chain reaction (PCR) for bacterial detection in a whole blood sample were performed. MEASUREMENTS AND MAIN RESULTS: Fifty-seven cases (patients with suspected infection) and 36 controls (patients with no suspected infection) were recruited during this period; 51.6% were female. Median age was 6 months (interquartile range [IQR], 0–13 mo), and median weight was 5 kg (IQR, 3.5–9.5 kg). From the cases, 33% (19/57) had a confirmed BSI with positive blood culture; 52% were Gram-negative bacilli, and 48% were Gram-positive cocci. Thirty-three percentage (19/57) had a positive PCR with only a 26% (five cases) of concordance between PCR result and blood culture (three bacteremias for Klebsiella pneumoniae, one for Serratia marcescens, and one for Pseudomonas). CONCLUSIONS: Multiple PCRs in whole blood samples did not appear to be more sensitive than blood cultures in this series. Better concordance was found with Gram-negative microorganisms.