Flow Cytometric Methods in the Detection of Neonatal Infection

Bacterial infection remains the main cause of neonatal morbidity and mortality. With clinical signs unspecific and little, its course is fulminant, and only early antibiotic therapy protects from death or major adverse sequelae. Methods: Conventional diagnostic tests have shortcomings and are only partly suitable to identify infected vs. non-infected newborns. There is a fast increasing demand for standardized flow cytometric techniques in the detection of neonatal infection which require minimal amounts of blood. Target cells are monocytes/ macrophages, granulocytes and NK cells. Results: The choice of receptors and interpretation of results need to be done carefully: A variety of receptors are expressed differently, basally or upon cytokine-mediated regulation, in full- or preterm neonates than in adults, and their expression is influenced by perinatal confounders. Examples are HLA-DR, CD80, CD86, CD16, CD32 receptors on monocytes/macrophages. Flow cytometric measurement of CD11b and CD64 expression on phagocytes combined with cytokine (IL-6 or IL-8) or C-reactive protein measurement in plasma or whole blood have turned out to be most sensitive and specific markers for detecting early- and late-onset bacterial infection. Conclusion: To date, no flow cytometric marker or set of markers is sensitive and specific enough to allow neonatologists to withhold antibiotic treatment of a sick neonate who is suspected to be infected.