Growth Requirements of N. Gonorrhoeae †

Routine methods for the isolation of Neisseria gonorrhoeae employ various complex media in conjunction with devices designed to supply an atmosphere of approximately 10 per cent carbon dioxide. Recent investigations7 of the CO2 requirement of N. gonorrhoeae have shown that various strains of this microorganism can be grown on a Casamino-salts-glucose agar medium in the absence of CO2, provided an extract of yeast is added. The apparent effect of yeast extract in eliminating the requirement for CO2 could be duplicated by a combination of hypoxanthine, uracil, and oxaloacetate; however, growth in air with this combination proved inferior to the growth with yeast extract alone. An investigation of the nature of the additional factors in yeast extract was undertaken. This report presents evidence of the necessity for tryptophan and biotin in the metabolism of N. gonorrhoeae and the role of oxaloacetic acid as a source of CO2. The recognition of the importance of CO2 and the stimulatory effect of yeast extract has made possible the development of a simplified medium and a new technique for the isolation of N. gonorrhoeae from clinical specimens.