Meningococcal phenotypic and genotypic characteristics and human antibody levels.

During a 2-month period in 1984, throat and blood samples were collected from 1,102 healthy persons of different ages living in the city of Tromsø, Norway. One hundred and eight persons (9.8%) were meningococcal carriers, but the carrier rate varied with sex and age. Twenty-nine isolates (26.9%) were of serogroup B, and 31 (28.7%) isolates contained the serotype 15 antigen. Sixty-eight (63.0%) isolates were nontypable, 49 (45.4%) were nongroupable, and 21 (19.4%) were sulfonamide resistant. All nine serotype 2a isolates and eight (25.8%) of the serotype 15 isolates were sulfonamide resistant. Only these eight serotype 15, sulfonamide-resistant isolates had a DNA fingerprint similar to that of the majority of systemic isolates of Neisseria meningitidis in Norway. The average level of antimeningococcal immunoglobulin G antibodies, as determined by a whole-bacterium enzyme immunoassay with a systemic B:15 meningococcal strain as the antigen, was low until 12 to 15 years of age and then steadily increased.