Comparison of broad range 16S rDNA PCR and BACTEC system for detection of neonatal sepsis

Bacterial sepsis is a feared complication of the newborn. A large proportion of infants admitted to the Neonatal Intensive Care Unit [NICU] for suspected sepsis receive treatment with potent systemic antibiotics while a diagnostic workup is in progress. The gold standard for detecting bacterial sepsis is blood culture. However, the sensitivity of blood culture is suspected to be low. Molecular assays for the detection of bacterial DNA in the blood represent possible new diagnostic tools for early identification of a bacterial cause. The aim of this study was to compare a broad range 16S rDNA PCR done on blood samples without prior enrichment to conventional BACTEC blood culture for detecting bacteria in blood samples from neonates with suspected sepsis. Fifty five neonates with clinically diagnosed sepsis were included in this study. A broad range 16S rDNA polymerase chain reaction [PCR] without preincubation was compared to conventional diagnostic work up for clinical sepsis, including BACTEC PEDS PLUS/F blood culture, for early determination of bacterial sepsis in each infant. Only 20 infants had a positive blood culture. Analysis by 16Sr DNA PCR revealed 21 samples positive for the presence of bacterial DNA. PCR failed to be positive in one sample from blood culture positive infant, and was positive in 2 samples with blood culture negative infants. Compared to blood culture the diagnosis of bacterial proven sepsis by PCR revealed 95.0% sensitivity, 94.3% specificity, 90.5% positive predictive value and 97.1% negative predictive value. PCR combined with blood culture revealed bacteria in 40.0% of the patients diagnosed with sepsis. There is a need for PCR as a method to quickly point out the infants with sepsis. However, uncertainty about a bacterial cause of sepsis was not reduced by the PCR result, reflecting that blood culture is irreplaceable at present, since pure isolates are essential for antimicrobial drug susceptibility testing