Preparation and stability of freeze-dried Neisseria gonorrhoeae cultures used for external quality control.

In 1976, the Center for Disease Control initiated an external quality control program for the isolation and identification of Neisseria gonorrhoeae. This program required microbial samples of sufficient stability for shipment to laboratories throughout the United States. The Centers for Disease Control undertook studies to determine the most appropriate media for the propagation of strains for freeze-drying, the cell-suspending media that would afford protection during and after freeze-drying, the most favorable growth conditions, the proper times and methods for harvesting cells, the appropriate lyophilization conditions, the critical residual moisture content, and the stability of samples. These studies resulted in the development of methods for preparing and testing freeze-dried samples suitable for shipment.