Vaccine-driven selection and the changing molecular epidemiology of Bordetella pertussis

Abstract

Pertussis remains one of the least controlled vaccine-preventable diseases despite high vaccine coverage in many countries. There are ongoing debates about the causes of its resurgence. Major changes have occurred in the Bordetella pertussis population since the introduction of vaccination. Currently circulating strains in Australia and many other developed countries are grouped in single nucleotide polymorphism (SNP) cluster I (also known as ptxP3 strains). The emergence and expansion of SNP cluster I has been associated with two major genetic changes in B. pertussis: a change in its pertussis toxin promoter (to ptxP3) which leads to increased pertussis toxin production and the change of the acellular vaccine pertactin gene allele to prn2. More recently, strains that lack pertactin have emerged independently in different lineages. The resurgence of pertussis in highly vaccinated populations can be, at least in part, explained by genetic changes that increase the fitness of circulating B. pertussis strains.