A chemically defined protein-free liquid medium for the cultivation of some species of Neisseria.

Chemically defined, protein-free, liquid culture media are needed for research with pathogenic bacteria and for the preparation of vaccines from them. Variations in growth or yield of organisms should be due only to differences in strain, and the medium itself should have little or no antigenic properties or toxicity. The medium should maintain the integrity of the bacterial species fully and it is particularly important that the complete antigenic complement of the organism should remain unaltered. The medium should be inexpensive and simple to prepare. Such a medium for the cultivation of some species of Neisseria, known to be fastidious, is described.In this new medium all the criteria are satisfied, and its freedom from sensitizing proteins makes it of particular value for use in man. Results of safety tests of vaccines prepared from Neisseria gonorrhoeae and N. meningitidis grown in this medium were encouraging. It should also be useful in studies on the physiological characteristics of the individual species.