The assessment of phagocytic and bactericidal activity of platelets and plasma bactericidal activity in late preterm newborns

Abstract

Background: The aim of the study was to compare the phagocytic and bactericidal properties of blood platelets and the plasma bactericidal activity in 66 late preterm (LPN) and 74 full-term newborns (FTN). Materials/Methods: Blood samples were collected from the umbilical artery. Bacteria of the Staphylococcus aureus ATCC 6538P were used for the tests. Results: Platelet counts in LPN vs FTN were the following: 225 vs 258.5 (x10³/μL), p = 0.003. The percentage of phagocytic platelets was the following: Me = 1.1 in LTN vs Me = 1.1 in FTN. The phagocytic index was the following: Me = 1 for both LPN and FTN. The phagocytic properties of platelets increased as the birth weight increased. The bactericidal activity of platelets was the following: Me = 0; (average = 0.7) in LPN vs Me = 0; (average = 0.8) in FTN. The median plasma bactericidal activity in LPN was 41.6 vs 43.8, in FTN, p = 0.027. The bactericidal capacity of plasma increased with increasing fetal age and birth weight of newborns. sP-selectin was: 63.9 ng/ml in LPN vs 71 ng/ml in FTN, p = 0.026. IL-6 in LPN was 3.6 vs 3.9 (pg/ml) in FTN, p = 0.02. Conclusion: Late preterm newborns have lower defensive capacity against infection than full-term newborns, due to lower platelets count, lower plasma bactericidal activity and lower sP-selectin concentration, which cooperates with neutrophils, monocytes in fighting against infection. All newborns had similar phagocytic and bactericidal properties of platelets.