Catalyzes the transfer of sialic acid from the substrate CMP-N-acetylneuraminate to the terminal galactose residue of the lacto-N-neotetraose branch of surface lipooligosaccharide (LOS), forming an alpha-2,3-sialyl linkage. Thus, functions in the sialylation of LOS, which plays a role in the evasion of the host immune response by protecting N.meningitidis from complement-mediated serum killing and from phagocytic killing by neutrophils. a beta-D-galactosyl-(1->4)-N-acetyl-beta-D-glucosaminyl derivative + CMP-N-acetyl-beta-neuraminate = an N-acetyl-alpha-neuraminyl-(2->3)-beta-D-galactosyl-(1->4)-N-acetyl-beta-D-glucosaminyl derivative + CMP + H(+) Bacterial outer membrane biogenesis; lipooligosaccharide biosynthesis. Homodimer. Belongs to the glycosyltransferase 52 family.