From these, we selected four peptides (αS1-casein [157–163], αS1-casein [157–165], β-casein [153–159] and plasminogen [591–597]) with varying prediction scores to synthesize and test for antimicrobial action against four strains of bacteria previously observed in culture-positive blood samples of preterm infants in neonatal intensive care units with sepsis and/or NEC. Here, PTGDR is linked to necrotizing enterocolitis.