KINETICS OF CONVERSION OF NEISSERIA-GONORRHOEAE TO RESISTANCE TO COMPLEMENT BY CYTIDINE 5'-MONOPHOSPHO-N-ACETYL NEURAMINIC ACID

Freshly isolated gonococci upon subculture are readily lysed by normal human serum although a few strains remain inherently resistant to the complement activity. The sensitive gonococci can be converted to seru m resistance by incubation with a host derived factor referred to as c ytidine 5'-monophospho-N-acetylneuraminic acid (CMP-NANA). These gonoc occi resist complement mediated killing due to their sialylation of an epitope structure on a component of lipo-oligosaccharide (LOS). In th e present study, the kinetics of conversion to serum resistance by the action of sialyltransferase (STase) in Neisseria gonorrhoeae was foll owed with very low concentrations of CMP-NANA. This conversion could n ot be perceived at 2 x 10(-3) nmol.ml(-1) but was fully attainable fro m 8 x 10(-3) to 2 x 10(-2) nmol.ml(-1) CMP-NANA. When pretreated up to 100 min in presence of the very low concentration of 2 x 10(-3) nmol. ml(-1), a potentiating effect on the conversion of gonococci by 2 x 10 (-2) nmol.ml(-1) was observed in relation to the time of preincubation . This action was abolished after exposure to a subinhibitory concentr ation of chloramphenicol (0.5 mu g.ml(-1)). The gonococci recovered th eir ability to convert to serum resistance following adequate washing. The potential for increase in STase activity should be of interest fo r understanding the conversion from a serum sensitive to a serum resis tance state.