[Study of long-term and multiple carriage of Neisseria meningitidis in a healthy population using molecular biology methods].

The aim of the study was to investigate the long-term duration and multiple carriage of Neisseria meningitidis in a healthy population. In this prospective study, 206 students at the age of 15 to 19 years were monitored from October 2002 to March 2003. Nasopharyngeal and laryngeal swabs were sampled in one-month intervals and cultured on a selective medium. All colonies detected in primary culture were saved for the study, a maximum of 20 colonies in cases of massive growth. A total of 1,242 isolates were obtained, all of them being examined by a molecular biology method RAPD (randomly amplified polymorphic DNA analysis). By other methods (determination of phenotype by slide agglutination and whole-cell ELISA test, the determination of sequence type, ST by multilocus sequence typing, testing of susceptibility to antibiotics) were always tested the first isolates from individual carriers and isolates from the same carrier with different RAPD characteristics, being 35 altogether. There were thirty three carriers of N. meningitidis detected among the 206 students (16%). The carriage of N. meningitidis was of long-term duration. The study of strains of N. meningitidis with molecular biology methods made it clear that the carrier population of meningococci is heterogeneous. The population of carrier meningococci was of clonal character and mostly non-virulent ST-complexes were detected. Multiple carriage of different clones of N. meningitidis is rare and usually of short-term duration. The colonization of upper respiratory tract by a single clone of N. meningitidis does not protect from colonization by other clone.