Bacteriocins in Neisseria meningitidis. Screening of systemic patient strains and pharyngeal isolates from healthy carriers.

Systemic meningococcal isolates and meningococci from healthy pharyngeal carriers in Norway were screened for production of growth antagonistic substances. Seven (4.9%) of a total of 142 systemic strains and 3 (2.1%) of 140 carrier isolates spontaneously released diffusible growth antagonistic substances. Properties shown by these substances complied with the criteria used in the definition of a bacteriocin. A cluster of producers among systemic strains registered during the first half of 1975 in North Norway (13.5% of the isolates) was observed, coinciding with the peak in incidence of meningococcal disease of the Norwegian epidemic starting in that region. Among more recent isolates, producers occurred at approximately the same rate in systemic strains (2.5%) as in carrier isolates. The meningocin-producing isolates detected were either of serogroup A and generally sulfonamide-resistant, or serogroup B and sulfonamide-sensitive. The group A strains isolated from disease cases in North Norway during the first half of 1975 were mostly sulfonamide-resistant. Except for the producers, all these strains revealed distinctly higher sensitivity to meningocin than did serogroup B sulfonamide-resistant strains, which became predominant among meningococci causing disease in Norway from that time on.