TLR4 and necrotizing enterocolitis: In premature neonates, the association between hyperoxia and postnatal growth restriction, alters the microbiota of the distal small bowel and cecum, leading to an increase in pro-inflammatory Gram-negative Enterobacteriaceae: the recognition of lipopolysaccharide in the cell wall of Enterobacteriaceae by the host TLR-4 is important in the pathogenesis of necrotizing enterocolitis.