Comparison of PCR, fluorescent in situ hybridization and blood cultures for detection of bacteremia in children and adolescents during antibiotic therapy

The gold standard in microbiological diagnostics of bacteremia is a blood culture in automated systems. This method may take several days and has low sensitivity. New screening methods that could quickly reveal the presence of bacteria would be extremely useful. The objective of this study was to estimate the effectiveness of these methods with respect to blood cultures in the context of antibiotic therapy. Blood samples from 92 children with sepsis were analyzed. Blood cultures were carried out in standard automated systems. Subsequently, FISH (Fluorescent In-Situ Hybridization) and nested multiplex-real-time-PCR (PCR) were performed. Blood cultures, FISH and PCR yielded positive results in 18%, 39.1%, and 71.7% of samples, respectively. Significant differences were found between the results obtained through culture before and after induction of antibiotherapy: 25.5% vs. 9.7%. There was no significant difference in FISH and PCR results in relation to antibiotics. The three methods employed demonstrated significant differences in detecting bacteria effectively. Time to obtain test results for FISH and PCR averaged 4–5 hours. FISH and PCR allow to detect bacteria in blood without prior culture. These methods had high sensitivity for the detection of bacteremia regardless of antibiotherapy. They provide more timely results as compared to automated blood culture, and may be useful as rapid screening tests in sepsis.