Potential of Molecular Culture in Early Onset Neonatal Sepsis Diagnosis: A Proof of Principle Study

Abstract

Delay in the time-to-positivity of a peripheral blood culture (PBC), the gold standard for early onset neonatal sepsis (EOS) diagnosis, has resulted in excessive use of antibiotics. In this study, we evaluate the potential of the rapid Molecular Culture (MC) assay for quick EOS diagnosis. In the first part of this study, known positive and spiked blood samples were used to assess the performance of MC. In the in vivo clinical study, the second part of this study, all infants receiving antibiotics for suspicion of EOS were included. At initial EOS suspicion, a blood sample was collected for PBC and MC. MC was able to detect bacteria present in the spiked samples even when the bacterial load was low. In the clinical study, MC was positive in one infant with clinical EOS (Enterococcus faecalis) that was not detected by PBC. Additionally, MC was positive in two infants without clinical sepsis (Streptococcus mitis and multiple species), referred to as contamination. The other 37 samples were negative both by MC and PBC. MC seems to be able to detect bacteria even when the bacterial load is low. The majority of MC and PBC results were comparable and the risk for contamination and false positive MC results seems to be limited. Since MC can generate results within 4 h following sampling compared with 36-72 h in PBC, MC may have the potential to replace conventional PBC in EOS diagnostics in order to guide clinicians on when to discontinue antibiotic therapy several hours after birth.

Keywords: IS-pro; diagnosis; early onset sepsis; molecular culture; neonates.

Figure 1

A linear correlation can be seen between Ct values as measured by specific qPCR and MC load, as measured by Log₂ transformed Relative Fluorescence Units (RFU) (R² = 0.78, p = 2.92 × 10⁻⁵).

Figure 2

Comparison of DNA extraction with (P) or without (N) Polaris pre-treatment. The test was performed on three replicates on three different bacterial species, Staphylococcus haemolyticus (Sh), Proteus mirabilis (Pm) and Escherichia coli (Ec). Molecular Culture loads are expressed in Relative Fluorescence Units (RFU). Adding Polaris pre-treatment resulted in significantly increased detected loads.