Raymond S W Tsang1, Michelle Shuel2, Frances B Jamieson3, Steven Drews4, Linda Hoang5, Greg Horsman6, Brigitte Lefebvre7, Shalini Desai8, Monique St-Laurent8. 1. National Microbiology Laboratory, Public Health Agency of Canada, 1015 Arlington Street, Winnipeg, Manitoba, R3E 3R2, Canada. Electronic address: raymond.tsang@phac-aspc.gc.ca. 2. National Microbiology Laboratory, Public Health Agency of Canada, 1015 Arlington Street, Winnipeg, Manitoba, R3E 3R2, Canada. 3. Public Health Ontario, Toronto, Ontario, Canada; Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada. 4. ProvLab Alberta Health Services, Calgary, Alberta, Canada; Department of Microbiology, Immunology, and Infectious Diseases, University of Calgary, Alberta, Canada. 5. Public Health Microbiology and Reference Laboratory, BC Public Health Microbiology and Reference Laboratory, Vancouver, British Columbia, Canada. 6. Saskatchewan Disease Control Laboratory, Regina, Saskatchewan, Canada. 7. Laboratoire de Santé Publique du Québec, Sainte-Anne-de-Bellevue, Québec, Canada. 8. Centre for Immunisation and Respiratory Infectious Diseases, Pubic Health Agency of Canada, Ottawa, Ontario, Canada.
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.
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: Alex Marchand-Austin; Raymond S W Tsang; Jennifer L Guthrie; Jennifer H Ma; Gillian H Lim; Natasha S Crowcroft; Shelley L Deeks; David J Farrell; Frances B Jamieson Journal: J Clin Microbiol Date: 2017-02-22 Impact factor: 5.948
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