A NEW SOLID MEDIUM FOR THE ISOLATION OF NEISSERIA GONORRHOEAE.
Biological products have been widely used in media intended for the primary isolation of Neisseria gonorrhoeae. Most of these substances are expensive and, in some places, difficult to procure. Ascitic fluid, which has been extensively used, is becoming increasingly rare. On the other hand, attempts to replace these biological substances by chemical compounds have met with little success, and a satisfactory synthetic medium does not exist. The authors describe the laboratory preparation of a reproducible medium which does not contain any fresh biological substances. It was developed from a routine "chocolate medium" which contained ascitic fluid and heated horse blood. Experiments with sparsely growing fresh laboratory strains showed that the ascitic fluid could be replaced by a combination of yeast and liver autolysates and the horse blood by haemoglobin. This Haemoglobin-Yeast-Liver (HYL) medium proved to be well suited for the primary isolation of N. gonorrhoeae and preliminary experiments indicated that it might also be suitable for use as a reference medium in sensitivity determinations. Attempts to use yeast and liver autolysates to replace ascitic fluid in a fermentation medium which did not contain blood or haemoglobin were less successful. Germination on the modified medium was relatively poor and it seems that the addition of a protective agent, such as albumin or starch, will be necessary.