title: Phenotypic and genotypic characterization of meningococcal carriage and disease isolates in Burkina Faso after mass vaccination with a serogroup a conjugate vaccine.
abstract: BACKGROUND
  The conjugate vaccine against serogroup A Neisseria meningitidis (NmA), MenAfriVac, was first introduced in mass vaccination campaigns of the 1-29-year-olds in Burkina Faso in 2010. The aim of this study was to genetically characterize meningococcal isolates circulating in Burkina Faso before and up to 13 months after MenAfriVac mass vaccination.
  
  
  METHODS
  A total of 1,659 meningococcal carriage isolates were collected in a repeated cross-sectional carriage study of the 1-29-year-olds in three districts of Burkina Faso in 2010 and 2011, before and up to 13 months after mass vaccination. Forty-two invasive isolates were collected through the national surveillance in Burkina Faso in the same period. All the invasive isolates and 817 carriage isolates were characterized by serogroup, multilocus sequence typing and porA-fetA sequencing.
  
  
  RESULTS
  Seven serogroup A isolates were identified, six in 2010, before vaccination (4 from carriers and 2 from patients), and one in 2011 from an unvaccinated patient; all were assigned to sequence type (ST)-2859 of the ST-5 clonal complex. No NmA carriage isolate and no ST-2859 isolate with another capsule were identified after vaccination. Serogroup X carriage and disease prevalence increased before vaccine introduction, due to the expansion of ST-181, which comprised 48.5% of all the characterized carriage isolates. The hypervirulent serogroup W ST-11 clone that was responsible for most of meningococcal disease in 2011 and 2012 was not observed in 2010; it appeared during the epidemic season of 2011, when it represented 40.6% of the serogroup W carriage isolates.
  
  
  CONCLUSIONS
  Successive clonal waves of ST-181 and ST-11 may explain the changing epidemiology in Burkina Faso after the virtual disappearance of NmA disease and carriage. No ST-2859 strain of any serogroup was found after vaccination, suggesting that capsule switching of ST-2859 did not occur, at least not during the first 13 months after vaccination.
authors.affiliation: Norwegian Institute of Public Health, Oslo, Norway. paul.kristiansen@fhi.no
authors.forename: Paul A
authors.initials: PA
authors.lastname: Kristiansen
authors.forename: Absatou Ky
authors.initials: AK
authors.lastname: Ba
authors.forename: Idrissa
authors.initials: I
authors.lastname: Sanou
authors.forename: Abdoul-Salam
authors.initials: AS
authors.lastname: Ouédraogo
authors.forename: Rasmata
authors.initials: R
authors.lastname: Ouédraogo
authors.forename: Lassana
authors.initials: L
authors.lastname: Sangaré
authors.forename: Fabien
authors.initials: F
authors.lastname: Diomandé
authors.forename: Denis
authors.initials: D
authors.lastname: Kandolo
authors.forename: Jennifer Dolan
authors.initials: JD
authors.lastname: Thomas
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Clark
authors.forename: Marc
authors.initials: M
authors.lastname: Laforce
authors.forename: Dominique A
authors.initials: DA
authors.lastname: Caugant
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016667:Bacterial Capsules / Q000235:genetics; D002050:Burkina Faso; D002353:Carrier State / Q000382:microbiology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005838:Genotype; D006801:Humans; D007223:Infant; D032541:Mass Vaccination; D008589:Meningococcal Infections / Q000382:microbiology* / Q000517:prevention & control; D022401:Meningococcal Vaccines / Q000008:administration & dosage*; D008826:Microbial Sensitivity Tests; D009345:Neisseria meningitidis / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D010641:Phenotype
chemical_list: D000900:Anti-Bacterial Agents; D022401:Meningococcal Vaccines
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