Liberation of endotoxin during growth of Neisseria meningitidis in a chemically-defined medium

Modified medium 199 is well suited to the growth of meningococci if rich growth is not necessary. The bacteria were very sensitive to changes in pH and needed a good buffer capacity of the medium. Four strains of Neisseria meningitidis were studied. After the stationary phase had been reached, the vital cell count decreased relatively slowly. However, the total cell count remained unchanged for at least 12 hours. The standardized E. coli endotoxin could be detected easily by the Limulus lysate test in different protein-free, pH-adjusted and ion-balanced liquids, and the determination of endotoxin was reproducible. The Limulus lysate test was more sensitive than the rabbit pyrogen test as regards meningococcal endotoxin. Liberation of endotoxin during growth in modified medium 199 varied with strain and growth conditions. Repeated investigations showed the same pattern of growth and endotoxin liberation for each strain, also under other growth conditions. When sonicating the bacteria, high yields of endotoxin were obtained from each strain.