Carried meningococci in the Czech Republic: A diverse recombining population

Population and evolutionary analyses of pathogenic bacteria are frequently hindered by sampling strategies that concentrate an isolates from patients dth invasive disease. This is especially so for the gram-negative diplococc us Neirseria meningitidis, a cause of septicemia and meningitis worldwide. Meningococcal isolate collections almost exclusively comprise organisms ori ginating from patients with invasive meningococcal disease, although this b acterium is a commensal inhabitant of the human nasopharynx and very rarely causes pathological effects. In the present study, molecular biology-based techniques were used to establish the genetic relationships of 156 meningo cocci isolated from healthy young adults in the Czech Republic during 1993. None of the individuals sampled had known links to patients with invasive disease. Multilocus sequence typing (MLST) showed that the bacterial popula tion was highly diverse, comprising 71 different sequence types (STs) which were assigned to 34 distinct complexes or lineages. Three previously ident ified hyperinvasive lineages were present: 26 isolates (17%) belonged to th e ST-41 complex (lineage 3); 4 (2.6%) belonged to the ST-11 (electrophoreti c type [ET-37]) complex, and 1 (0.6%) belonged to the ST-32 (ET-5) complex. The data were consistent with the view that most nucleotide sequence diver sity resulted from the reassortment of alleles by horizontal genetic exchan ge.