[Researches on the production of inhibitory substances by strains of "N. meningitidis" (author's transl)].

The possibility to produce some inhibitory substances has been researched in 85 strains of N. meningitidis belonging to different serogroups. By the double layer agar method, 9 of these strains have inhibited the growth of one or more indicator strains. We had the best results at 37 degrees C and 30 degrees C in tests made incubating 3 producer strains in different experiment conditions; the "Brain heart infusion agar" and the "Heart infusion agar" were the best and fittest culture media, used for the production of these substances. Several attempts to get the production of bacteriocins in liquid culture media have always given negative results, both by spontaneous growing and by ultraviolet irradiation and mitomycin induction. We were able to get 3 among these substances from as many strains of N. meningitidis (from the 85 tested) in the supernatant, only growing the strains in soft agar and centrifuging these growths. So these 3 bacteriocins had inhibited the growth of the 92% of the tested N. meningitidis, but they were inactive towards 296 bacterial strains belonging to Gram-positive and Gram-negative species (including the 15 strains of Shigella and E. coli given as indicators in the research of colicins), 70 strains of Mycoplasma and 9 L-forms of Pr. mirabilis and of St. aureus. Only 3 L-forms obtained from as many strains of N. meningitidis resulted to be inhibited by the three bacteriocins.