Strunk T, Hibbert J, Doherty D, et al. - Given the common encounter to late-onset sepsis (LOS) with Staphylococcus epidermidis in preterm infants, researchers sought to describe the ontogeny of cytokine responses to live S. epidermidis in preterm infants with and without subsequent Gram-positive LOS. They conducted a prospective observational cohort study of 129 infants (mean gestational age 26.2 weeks, mean BW 887g) who had blood sampling on days 1, 7, 14, 21 and 28 of life. Among these, 23 infants (17.8%) had confirmed LOS with Gram-positive organisms and 15 infants (11.6%) had clinical sepsis, with a median onset at 13 and 15 days, respectively. Outcomes suggest that infants with LOS exhibit impaired cytokine responses to live S. epidermidis challenge and this impairment precede the onset of clinical illness. High-risk preterm infants at greatest risk of LOS could be recognized via quantifying pathogen-specific cytokine responses at day 7.