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Appearance of Fim3 and ptxP3-Bordetella pertussis strains, in two regions of Sweden with different vaccination
Abdolreza Advani1, Lennart Gustafsson, Christina Ahrén
1Swedish Institute for Communicable Disease Control, SE-171 82 Solna, Sweden. reza.advani@smi.se
Insights
A pertussis vaccine with only one antigen led to higher pertussis incidence. This was linked to the rise of more virulent Bordetella pertussis strains (ptxP3) in the vaccinated area, highlighting the need for effective vaccine components.
Area of Science:
- Microbiology
- Immunology
- Epidemiology
Background:
- A mono-component pertussis toxoid (PT) vaccine was associated with higher pertussis incidence in Gothenburg compared to a multi-antigen vaccine used elsewhere in Sweden.
- This difference in incidence prompted an investigation into the circulating Bordetella pertussis strains.
Purpose of the Study:
- To compare Bordetella pertussis populations in Gothenburg and the Rest of Sweden to understand the increased pertussis incidence.
- To investigate the role of specific B. pertussis strain characteristics in vaccine effectiveness.
Main Methods:
- Bordetella pertussis strains were analyzed for fimbrial serotype (Fim), PFGE-type, and pertussis toxin promoter allele type (ptxP).
- Strain typing was performed on samples from children in Gothenburg and the Rest of Sweden between 1997 and 2006.
Main Results:
- Pertussis toxin promoter allele type ptxP1 strains were replaced by ptxP3 strains, which produce more pertussis toxin.
- Fimbrial serotype 3 (Fim3) and ptxP3 strains emerged earlier and were more frequent in Gothenburg compared to the Rest of Sweden.
- A strong association was observed between PFGE-profile and the ptxP3 allele.
Conclusions:
- The increased prevalence of more virulent ptxP3 strains in Gothenburg may explain the higher pertussis incidence observed with the mono-component vaccine.
- Strain typing is crucial for understanding immunity-associated selection of microbial subtypes and changes in infectious disease incidence.
- Vaccine composition significantly impacts the selection and prevalence of Bordetella pertussis virulence factors.
Abstract:
After introduction of a mono-component vaccine, containing only pertussis toxoid (PT), the incidence of pertussis was significantly higher in the Gothenburg area among children during the period October 1, 1997 until end of 2006 compared to the Rest of Sweden where a vaccine containing PT and two other pertussis antigens was used. To investigate a possible cause of this difference, the Bordetella pertussis populations in both regions were compared by determining the fimbrial serotype (Fim), the PFGE-type and the pertussis toxin promoter allele type (ptxP). Strains with the ptxP1 allele were successively replaced by ptxP3 strains producing more pertussis toxin. In Gothenburg compared to the Rest of Sweden, Fim3 and ptxP3 strains were observed earlier and reached higher frequencies in the studied period. Since ptxP3 strains have been shown to be more virulent, their higher prevalence may have contributed to the higher incidence of pertussis in the Gothenburg area. In addition we found a high degree of linkage between PFGE-profile and ptxP3. Our results highlight the importance of strain typing to gain insight into the mechanisms of immunity-associated selection of microbial subtypes and the causes of changes in incidences of infectious diseases.
