Cytidine 5′-monophospho-N-acetyl neuraminic acid and a low molecular weight factor from human blood cells induce lipopolysaccharide alteration in gonococci when conferring resistance to killing by human serum

Abstract

Recently evidence has been obtained that a minute amount of cytidine 5′-monophospho-N-acetyl neuraminic acid (CMP-NANA) or a closely related compound is the low M r factor in human red blood cells which induces Neisseria gonorrhoeae (BS4(agar)) to resistance to killing by fresh human serum. Induction of gonococci to resistance by both CMP-NANA and semi-purified low M r factor from red blood cells was accompanied by a 35–55% reduction of silver staining of lipopolysaccharide separated in SDS-PAGE gels of proteinase K digests. These alterations in lipopolysaccharide are probably responsible for conferring serum resistance. However, lipopolysaccharide-containing digests from resistant as well as from susceptible gonococci neutralised serum bactericidal activity. These observations may have wider implications since CMP-NANA is a sialylating agent wide-spread in mammalian tissues and LPS is ubiquitous amongst Gram-negative pathogens.