title: Pertactin-negative Bordetella pertussis strains in Canada: characterization of a dozen isolates based on a survey of 224 samples collected in different parts of the country over the last 20 years.
abstract: OBJECTIVE
  To detect and characterize pertactin-negative Bordetella pertussis in Canada, especially for isolates collected in recent years.
  
  
  METHODS
  A total of 224 isolates from the years 1994-2013 were screened by Western immuno-blot for expression of pertactin. Pertactin-negative isolates were characterized by serotyping, pulsed-field gel electrophoresis (PFGE), and genotyping of their pertactin, fimbriae 3, pertussis toxin subunit 1, and pertussis toxin gene promoter region, as well as the complete sequence of the pertactin gene.
  
  
  RESULTS
  Twelve isolates were pertactin-negative, giving an overall prevalence of 5.4%. However, no such isolate was found prior to 2011 and 17.8% of 62 isolates examined in 2012 were pertactin-negative. Ten pertactin-negative isolates contained a significant mutation in their pertactin (prn) genes. IS481 was found in the prn genes of eight isolates, while a single point mutation occurred either in the coding region (resulting in a premature stop codon) or in the promoter region (preventing gene transcription) in two other isolates. PFGE analysis also showed multiple profiles suggesting that several independent genetic events might have led to the emergence of these pertactin-negative strains rather than expansion of a single clone.
  
  
  CONCLUSIONS
  As reported elsewhere, pertactin-negative B. pertussis has emerged in Canada in recent years, notably in 2012. This coincided with an increase in pertussis activity in Canada. A further systematic study with a larger geographical representative sample is required to determine how these vaccine-negative strains may contribute to the overall changing epidemiology of pertussis in Canada.
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, 1015 Arlington Street, Winnipeg, Manitoba, R3E 3R2, Canada. Electronic address: raymond.tsang@phac-aspc.gc.ca.
authors.forename: Raymond S W
authors.initials: RS
authors.lastname: Tsang
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, 1015 Arlington Street, Winnipeg, Manitoba, R3E 3R2, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Shuel
authors.affiliation: Public Health Ontario, Toronto, Ontario, Canada; Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Frances B
authors.initials: FB
authors.lastname: Jamieson
authors.affiliation: ProvLab Alberta Health Services, Calgary, Alberta, Canada; Department of Microbiology, Immunology, and Infectious Diseases, University of Calgary, Alberta, Canada.
authors.forename: Steven
authors.initials: S
authors.lastname: Drews
authors.affiliation: Public Health Microbiology and Reference Laboratory, BC Public Health Microbiology and Reference Laboratory, Vancouver, British Columbia, Canada.
authors.forename: Linda
authors.initials: L
authors.lastname: Hoang
authors.affiliation: Saskatchewan Disease Control Laboratory, Regina, Saskatchewan, Canada.
authors.forename: Greg
authors.initials: G
authors.lastname: Horsman
authors.affiliation: Laboratoire de Santé Publique du Québec, Sainte-Anne-de-Bellevue, Québec, Canada.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Lefebvre
authors.affiliation: Centre for Immunisation and Respiratory Infectious Diseases, Pubic Health Agency of Canada, Ottawa, Ontario, Canada.
authors.forename: Shalini
authors.initials: S
authors.lastname: Desai
authors.affiliation: Centre for Immunisation and Respiratory Infectious Diseases, Pubic Health Agency of Canada, Ottawa, Ontario, Canada.
authors.forename: Monique
authors.initials: M
authors.lastname: St-Laurent
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D001886:Bordetella pertussis / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D002170:Canada; D005838:Genotype; D006801:Humans; D009154:Mutation; D037342:Pertussis Toxin / Q000235:genetics; D012703:Serotyping; D010566:Virulence Factors, Bordetella / Q000235:genetics* / Q000378:metabolism; D014917:Whooping Cough / Q000453:epidemiology / Q000382:microbiology
chemical_list: D001425:Bacterial Outer Membrane Proteins; D010566:Virulence Factors, Bordetella; C068929:pertactin; D037342:Pertussis Toxin
keywords: Bordetella pertussis; Molecular epidemiology; Pertactin-negative