Three types of growth inhibition among strains of Neisseria meningitidis isolated from patients in Norway.

A survey has been made of Neisseria meningitidis strains isolated from patients in order to determine the prevalence of diffusible growth inhibitory substances active against other meningococci. Three types of growth inhibitory activity could be distinguished. The first type was release in cultures of nearly all strains after treatment with chloroform vapour. This activity inhibited all meningococci tested, including the donor strains. The properties were similar to those of the non-specific growth inhibitors observed among most strains of N. gonorrhoeae. The second type was demonstrated in cultures from four strains among 215 strains tested and may be present in a fifth strain. Bactericidal activity with high strain specificity was spontaneously released from cultures of the four strains. This type of activity was found to fit the description of a bacteriocin. The third type of inhibition was observed in one strain among the 215 strains tested. Cultures of this strain spontaneously released bacteriostatic activity. Products from the strain could inhibit almost all meningococcal strains except the donor strain itself. This activity was not entirely blocked by bovine serum albumin; it was not abolished by pronase and it was not stopped by dialysis membranes with cut-off 12000.