Analysis of Bordetella pertussis clinical isolates circulating in European countries during the period 1998-2012

Abstract

Despite more than 50 years of vaccination, pertussis is still an endemic disease, with regular epidemic outbreaks. With the exception of Poland, European countries have replaced whole-cell vaccines (WCVs) by acellular vaccines (ACVs) in the 1990s. Worldwide, antigenic divergence in vaccine antigens has been found between vaccine strains and circulating strains. In this work, 466 Bordetella pertussis isolates collected in the period 1998-2012 from 13 European countries were characterised by multi-locus antigen sequence typing (MAST) of the pertussis toxin promoter (ptxP) and of the genes coding for proteins used in the ACVs: pertussis toxin (Ptx), pertactin (Prn), type 2 fimbriae (Fim2) and type 3 fimbriae (Fim3). Isolates were further characterised by fimbrial serotyping, multi-locus variable-number tandem repeat analysis (MLVA) and pulsed-field gel electrophoresis (PFGE). The results showed a very similar B. pertussis population for 12 countries using ACVs, while Poland, which uses a WCV, was quite distinct, suggesting that ACVs and WCVs select for different B. pertussis populations. This study forms a baseline for future studies on the effect of vaccination programmes on B. pertussis populations.

Fig. 1

Frequencies of the prn alleles in the period 1998–2012. Isolates were aggregated in three periods, 1998–2001, 2002–2006 and 2007–2012. a Allele frequencies in the 12 pooled countries: Belgium, the Czech Republic, Denmark, Finland, France, Germany, Ireland, Norway, Spain, Sweden, the Netherlands and the United Kingdom. b Allele frequencies in Poland. Due to the limited availability of Polish isolates in the period 2007–2012 (n = 2), no data are included for this period. The percentages and number of strains analysed in the different periods are indicated

Fig. 2

Frequencies of the ptxP alleles in the period 1998–2012. See caption of Fig. 1 for further details

Fig. 3

Frequencies of the fim2 alleles in the period 1998–2006 in Poland. Two periods are indicated, 1998–2001 and 2002–2006. Due to the limited availability of Polish isolates in 2007–2012 (n = 2), no data are included for this period. In the remaining 12 countries, only fim2-1 was observed, with the exception of Belgium, where one fim2-2 isolate was identified

Fig. 4

Frequencies of the fim3 alleles in the period 1998–2012. See caption of Fig. 1 for further details

Fig. 5

Frequencies of the serotypes in the period 1998–2012. a Serotype frequencies of the 11 pooled countries; Belgium, the Czech Republic, Denmark, Finland, France, Germany, Norway, Spain, Sweden, the Netherlands and the United Kingdom. b Serotype frequencies in Ireland. c Serotype frequencies in Poland. See caption of Fig. 1 for details

Fig. 6

Frequencies of the predominating multi-locus variable-number tandem repeat analysis (MLVA) types in the period 1998–2012. See caption of Fig. 1 for further details

Fig. 7

Frequencies of the predominating pulsed-field gel electrophoresis (PFGE) types in the period 1998–2012. See caption of Fig. 1 for further details