Abstract
Endotoxin liberation, encapsulation and growth was studied in 123 isolates of Neisseria meningitidis. Free endotoxin appeared in culture filtrates during exponential growth. Menin-gococci with free endotoxin titre >102 (E+) showed a higher mean number of viable bacterial counts (CFU/ml) during growth than isolates with titre <102 (E-), p<0.001. Differences in endotoxin liberation was, however, far more pronounced than what was indicated by growth differences alone. E+ property and increased growth rate was significantly more often found among encapsulated than non-encapsulated meningococci. Within the serogroup B isolates, there tended to be a higher mean number of CFU/ml during growth in E+ than E− meningococci, particularly among carrier isolates studied separately (p=0.009). Case isolates of B meningococci, which had generally a higher amount of capsular material and a higher proportion of E+ strains, had also higher mean CFU/ml than B carrier isolates. This indicates that the endotoxin liberation and growth may be correlated to presence and amount of capsular polysaccharide. Endotoxin liberation, presence of capsular polysaccharide and growth ability are 3 factors which are likely to coincide in meningococci. This combination of properties may be of importance for the development of meningococcal disease.