title: Molecular characterization of invasive meningococcal isolates from countries in the African meningitis belt before introduction of a serogroup A conjugate vaccine.
abstract: BACKGROUND
  The serogroup A conjugate meningococcal vaccine, MenAfriVac, was introduced in mass vaccination campaigns in December 2010 in Burkina Faso, Mali and Niger. In the coming years, vaccination will be extended to other African countries at risk of epidemics. To document the molecular characteristics of disease-causing meningococcal strains circulating in the meningitis belt of Africa before vaccine introduction, the World Health Organization Collaborating Centers on Meningococci in Europe and United States established a common strain collection of 773 isolates from cases of invasive meningococcal disease collected between 2004 and 2010 from 13 sub-Saharan countries.
  
  
  METHODS
  All isolates were characterized by multilocus sequence typing, and 487 (62%) were also analyzed for genetic variation in the surface antigens PorA and FetA. Antibiotic susceptibility was tested for part of the collection.
  
  
  RESULTS
  Only 19 sequence types (STs) belonging to 6 clonal complexes were revealed. ST-5 clonal complex dominated with 578 (74.8%) isolates. All ST-5 complex isolates were remarkably homogeneous in their PorA (P1.20,9) and FetA (F3-1) and characterized the serogroup A strains which have been responsible for most epidemics during this time period. Sixty-eight (8.8%) of the 773 isolates belonged to the ST-11 clonal complex which was mainly represented by serogroup W135, while an additional 38 (4.9%) W135 isolates belonged to the ST-175 complex. Forty-eight (6.2%) serogroup X isolates from West Africa belonged to the ST-181 complex, while serogroup X cases in Kenya and Uganda were caused by an unrelated clone, ST-5403. Serogroup X, ST-181, emerged in Burkina Faso before vaccine introduction.
  
  
  CONCLUSIONS
  In the seven years preceding introduction of a new serogroup A conjugate vaccine, serogroup A of the ST-5 clonal complex was identified as the predominant disease-causing strain.
authors.affiliation: WHO Collaborating Centre for Reference and Research on Meningococci, Norwegian Institute of Public Health, Oslo, Norway. dominique.caugant@fhi.no
authors.forename: Dominique A
authors.initials: DA
authors.lastname: Caugant
authors.forename: Paul A
authors.initials: PA
authors.lastname: Kristiansen
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.forename: Leonard W
authors.initials: LW
authors.lastname: Mayer
authors.forename: Muhamed-Kheir
authors.initials: MK
authors.lastname: Taha
authors.forename: Rasmata
authors.initials: R
authors.lastname: Ouédraogo
authors.forename: Denis
authors.initials: D
authors.lastname: Kandolo
authors.forename: Flabou
authors.initials: F
authors.lastname: Bougoudogo
authors.forename: Samba
authors.initials: S
authors.lastname: Sow
authors.forename: Laurence
authors.initials: L
authors.lastname: Bonte
mesh_terms: D017954:Africa South of the Sahara; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D014644:Genetic Variation; D006801:Humans; D008589:Meningococcal Infections / Q000145:classification / Q000188:drug therapy / Q000382:microbiology*; D009345:Neisseria meningitidis / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D018272:Porins / Q000235:genetics; D012703:Serotyping
chemical_list: D000900:Anti-Bacterial Agents; D018272:Porins; C057699:porin protein, Neisseria