Concordance of Blood Culture and Colonization in Neonates with Late Onset Sepsis on the Neonatal Intensive Care Unit

Background: Late-onset neonatal infection (LOS) is still an important cause of morbidity and mortality in neonates admitted to the Neonatal Intensive Care Unit (NICU). Weekly surveillance cultures of rectum and throat identify potential pathogen microorganisms colonizing the individual neonate. Individual surveillance culture results are taken into account to adjust the standard empirical antibiotic policy when starting antibiotics in case of suspicion of LOS.

Objective: To determine the degree of similarity between the causative microorganism of LOS in the blood culture and the pathogen microorganisms found in the individual surveillance cultures.

Methods: A retrospective, descriptive study, including all late-onset sepsis episodes with a positive blood culture from January 2009 to January 2019 at the NICU Isala, Zwolle. After data selection, 98 positive blood cultures were analysed and compared with the results of the surveillance cultures taken 1 week before the sepsis period.

Results: The causative agents in the blood culture corresponded in 61/98 (62%) to the results of the previously taken surveillance cultures, with the highest correspondence for the gram-negative causative agents (79%) and for Staphylococcus aureus (88%). If only positive surveillance cultures were analysed, the correspondence was higher: 82% for the total, 86% for gram-negative causative agents and 97% for Staphylococcus aureus. In case of lower gestational age or birth weight, we found an increase in similarity between positive blood culture and surveillance cultures.

Conclusion: There was a great similarity between the causative agent in the blood culture and pathogens found in positive surveillance culture in case of LOS, in particular for gram-negative pathogens and Staphylococcus aureus. Therefore, performing surveillance cultures seems useful for the individual patient and adjusting the empirical antibiotic policy on the base of known colonisations justified.