NFKB1 and necrotizing enterocolitis: Since innate immune response to the nascent microbiota, particularly to Gram-negative bacteria, could potentially contribute to NEC, we compared EC25 and other E. coli strains (K12 and several strains identified in this study) with regard to their ability to activate NF-κB, the key transcription factor in the innate immune response, in cultured enterocytes.