Intrapartum colonization with Streptococcus pneumoniae, early-onset sepsis and deficient specific neonatal immune responses

Background Intrapartum colonization with Streptococcus pneumoniae (S. pneumoniae) is a rare but important risk factor for severe courses of early-onset sepsis (EOS) in the newborn, as underlined in the case of a preterm infant born after 32 weeks of gestation described here. One potential explanation could be an immature immune response of the neonate to S. pneumoniae, however, immunological data in term and preterm infants are scarce. Methods To determine the neonatal immune responses to S. pneumoniae, flow-cytometry analysis of the cytokine production by CD14 cells was performed after full pathogen stimulation with S. pneumoniae (serotype 18C, derived from an EOS case described here) of cord blood of 10 term (37-41 gestational weeks) and 6 preterm (31-32 gestational weeks) neonates, compared to peripheral venous blood samples of 10 healthy adults in vitro. Results Neonatal cytokine responses of term and preterm infants to S. pneumoniae are diminished compared to adults. The quantities of cytokine expression were comparable to immune responses induced by other important gram-positive pathogens of EOS such as Streptococcus agalacticae. Conclusion Severe courses of EOS with S. pneumoniae may be attributed to remarkable deficiencies of the specific neonatal immune response. To protect the neonate from invasive pneumococcal disease, maternal immunization may be an important prevention strategy, as protective antibodies can be transferred through the placenta and vaccination of pregnant women may reduce colonization.