Relationship between phylogeny and the accumulation of mutations in virulence genes.

<p>The Maximum Parsimony tree was based on 85 SNPs and 198 Dutch strains isolated between 1949 and 2008. The 85 SNPs resolved the 198 strains in 31 sequence types (STs). Alleles for the pertussis toxin promoter (<i>ptxP</i>), the pertussis toxin A subunit (<i>ptxA</i>), pertactin (<i>prn</i>) and the serotype 3 fimbrial subunit (<i>fim3</i>) are indicated. The alleles <i>prn2</i> and <i>prn3</i> were combined as they are both non-vaccine types. Based on the <i>ptxP</i>, <i>ptxA</i>, <i>fim3</i> and <i>prn</i> alleles, seven allele types (ATs), I–VII, could be distinguished. Coloured dots represent distinct ATs and arrows indicate changes between ATs. ATs used for the production of the whole cell and acellular vaccines are blocked. Bootstrap values are indicated in the tree.