title: Influence of two vaccination campaigns on genetic diversity of invasive Neisseria meningitidis isolates in northern Spain (1997-2008).
abstract: BACKGROUND
  Neisseria meningitidis diversifies rapidly, due to its high recombination rates. The aim of this study was to analyze the possible impact of two vaccination campaigns (a once-off A/C polysaccharide vaccination campaign in people aged 18 months to 20 years old in 1997, and a meningococcal C conjugate vaccination campaign in children aged < or = 6 years old from 2000 to 2008) on diversification of the population of invasive isolates obtained between 1997 and 2008. All of the 461 available isolates were included (2, 319, 123, 11 and 6 belonging to serogroups A, B, C, Y and W-135, respectively).
  
  
  RESULTS
  The isolates were analyzed for diversity using multilocus sequence typing, eBURST and the S.T.A.R.T.2 program. One hundred and seven sequence types (ST) and 20 clonal complexes were obtained. Five different STs (ST11, ST8, ST33, ST1163 and ST3496) included 56.4% of the isolates. With the exception of ST11, all other STs were associated with a specific serogroup. Epidemic circulation of serogroup C ST8 isolates was detected in 1997-1998, as well as epidemic circulation of ST11 isolates (serogroups B and C) in 2002-2004. The epidemic behavior of serogroup B ST11 (ST11_B:2a:P1.5) was similar, although with lesser intensity, to that of ST11 of serogroup C. Although clonality increased during epidemic years, the overall diversity of the meningococcal population did not increase throughout the 12 years of the study.
  
  
  CONCLUSIONS
  The overall diversity of the meningococcal population, measured by the frequency of STs and clonal complexes, numbers of alleles, polymorphic sites, and index of association, remained relatively constant throughout the study period, contradicting previous findings by other researchers.
authors.affiliation: Microbiology Service and Reference Laboratory for Meningococcal Infections of the Basque Country, Hospital Donostia, San Sebastián, Spain.
authors.forename: Diego
authors.initials: D
authors.lastname: Vicente
authors.forename: Olatz
authors.initials: O
authors.lastname: Esnal
authors.forename: M José
authors.initials: MJ
authors.lastname: López de Goicoechea
authors.forename: Ramón
authors.initials: R
authors.lastname: Cisterna
authors.forename: Emilio
authors.initials: E
authors.lastname: Pérez-Trallero
mesh_terms: D000293:Adolescent; D015373:Bacterial Typing Techniques; D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D002999:Clone Cells; D014644:Genetic Variation; D006293:Health Promotion; D006801:Humans; D015994:Incidence; D007223:Infant; D008589:Meningococcal Infections / Q000453:epidemiology / Q000517:prevention & control; D009345:Neisseria meningitidis / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification*; D010507:Periodicity; D017422:Sequence Analysis, DNA; D013030:Spain / Q000453:epidemiology; D014611:Vaccination; D055815:Young Adult