Abstract
Miller 1 has described a method for the production of experimental meningococcal infection in mice. It consisted in brief of the use of a 6% mucin suspension buffered at 7.4 as a medium in which the organisms were suspended prior to intraperitoneal inoculation. More recently Miller has modified the technique of preparing the mucin. 2 A 5% suspension is now prepared, it is sterilized in the autoclave at 10–15 lb. pressure for 15 minutes, sterile dextrose solution is then added to a final concentration of 1%, and the pH adjusted to pH 7.4 with sterile buffer solution.
Using such a mucin suspension, the intraperitoneal virulence of meningococcus strains can be titrated, 1 , 3 and consistent results will be obtained when pure breeds of susceptible mice are employed. It has been found, in accord with Miller's work, that freshly isolated strains may kill when the cultures are diluted as far as 10-8, that is approximately 20 organisms. A brief report has been made elsewhere 3 on the application of this experimental meningococcal infection to the test of sera for their protective activity. That report dealt chiefly with the content of protective antibodies in the serum of carriers of the meningococcus and in the serum of normal individuals. The high protective value of some antimeningococcal sera was demonstrated but no titration was carried out.
In testing the intraperitoneal virulence of strains, 14 to 18-hour cultures on 10% rabbit's blood pneumococcus agar plates are washed off with normal saline and the suspension is diluted in saline and adjusted with a Gates turbidometer to the standard of 2,000,000,000 organisms per cc. Serial dilutions 1 :10 are made in mucin and range between 10-1 (200,000,000 organisms) and 10-8 (20 organisms).
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