Longitudinal study of meningococcal carrier rates in teenagers

To gain actual information concerning the oropharyngeal carriage of Neisseria meningitidis among teenagers aged 15-18 years in Germany especially in a region with increased incidence of meningococal-related diseases prompted the study. Each teenager was swabbed three times with an interval of 2 months between the examinations. The 901 recovered N. meningitidis strains were characterized using serological (serogrouping, serotyping/serosubtyping) and molecular methods (PCR, PFGE) each. The results of the study demonstrate an overall average carrier rate of 18.8% for the three collection periods. There were, however, significant differences between the carrier rates within a given school and of different towns and counties. Of all isolates, 60.6% were not serogroupable. Serogroup B dominated (12.3%), followed by serogroup Y (9.0%) and serogroup C (3.6%). After PCR-based serogrouping of not serogroupable strains the percentages for serogroups enhanced to 18.8% for B, 10.8% for Y and 4.1% for C. Serotyping led to 305 different phenotypes with the most common being 29E:NT:P1.2,5 followed by Y:14:NST. In the 6 study towns the number of different N. meningitidis clones (PFGE types) isolated, varied between 30 and 87. In Wenden, where a prolonged outbreak had taken place, serogroup C (14.8%) was predominant. Only in this town C:2a isolates were found, all belonging to the ST-11/ET-37 complex and 12/13 matched identically to the ET-15 clone. Of the colonized teenagers, 26.7% were carriers over at least 23 weeks, 22.6% with the same strain, 36.0% were carrier for at least 15 weeks. Over all three collection periods 36.7% of the adolescents acquired a new strain. The highest acquisition rate was related to PFGE type 12.