Endotoxin liberation and invasivity of Neisseria meningitidis.

The relationship between endotoxin liberation and invasiveness was studied in 50 strains of Neisseria meningitidis isolated from blood or cerebrospinal fluid (CSF) of 16 patients with invasive disease, from nasopharynx of 9 patients with upper respiratory tract symptoms, and from nasopharynx and rectum (1, serogroup W-135) in 25 persons examined for venereal disease. Meningococci varied in their ability to liberate endotoxin. Free endotoxin was partly a function of growth and seemed to be associated with certain properties of the individual strain. Strains isolated for patients with invasive disease liberated significantly more endotoxin than strains isolated from the venereal group (p less than 0.002). All 16 invasive strains were sulfonamide resistant, against 5/9 strains from patients with upper respiratory disease symptoms and only 4/25 strains from the venereal group. The difference between the invasive group and the venereal group was significant (p less than 0.002). Serogroup A, B, C meningococci liberated significantly more endotoxin than non-A, B, C strains (p = 0.01, and serogroup A, B, C strains isolated from nasopharynx tended to have a higher endotoxin release than non-A, B, C strains isolated from the same place (not significant). Serogroup B meningococci were most frequently isolated both from patients with invasive disease and from the nasopharynx of the persons examined for venereal disease. Serogroup B meningococci had significantly more free endotoxin when isolated from blood or CSF than when isolated from nasopharynx of presumably healthy persons (p = 0.002).