In vivo bacterial adherence of Pseudomonas aeruginosa to the immature ocular epithelium was mediated by a sialic (N-acetylneuraminic) acid (NANA) receptor. Saturation of binding sites on the bacterial surface by NANA prevented attachment of the organism to the epithelial cell membrane receptor. Additionally, a significant number of animals receiving NANA-treated organisms were protected from septicemia and death. In vivo protection studies showed excellent correlation with scanning electron microscopy, in that the number of adherent organisms at the corneal surface decreased dramatically in the presence of NANA. These studies exhibit a strong correlation with clinical cases of human infant ocular infection.