DYNAMICS OF THE MENINGOCOCCAL CARRIER STATE AND CHARACTERISTICS OF THE CARRIER STRAINS - A LONGITUDINAL-STUDY WITHIN 3 COHORTS OF MILITARY RECRUITS

Three cohorts of Danish male military recruits (n = 1069) were studied for pharyngeal meningococcal carriage during 3 months at different se asons: 39-47% of entrants were meningococcal carriers and the carriage rate remained constant over time and season. However, individual chan ges in the carrier state occurred frequently, and after 3 months 34% h ad changed carrier state on one or more occasions. Initially, a loss o f carriage predominated; on the other hand almost 20% of non-carriers had acquisition of meningococci within the first month. The serologica l phenotypes of the 670 carrier strains were compared with those of 26 1 invasive strains recovered concurrently from patients with meningoco ccal disease country-wide. Both carrier strains and invasive strains w ere phenotypically heterogeneous. Almost 60% of the invasive strains b elonged to three phenotypes: B:15:P1.7, 16, C:2a:P1.2, 5 and C:2b:P1.2 , 5. In contrast, these phenotypes only amounted to 32% of the carrier strains, among which no phenotype was found with a prevalence above 4 .9%. However, 30% of the carrier strains had serological phenotypes id entical to those of 80% of the invasive strains. Our results indicated that the transmission rate of potential pathogenic carrier strains di d not differ from that of other carrier strains.