Bordetella parapertussis isolates not expressing pertactin circulating in France.

Surprisingly, most Bordetella parapertussis isolates collected in France since 2007 do not express pertactin, owing to mutations in the structural gene encoding this protein. We used a 454 pyrosequencing strategy to study and compare the genetics of two B. parapertussis isolates (one expressing pertactin and one not expressing pertactin) and the reference strain. No region of difference was detected between the genomes of the two isolates and the genome of the reference strain. No increase in repeated sequences between both isolates was found, and there were very few sequence differences. Using cellular and animal models, we found no substantial difference between the pathogenicity of these B. parapertussis isolates, which is consistent with clinical data. The emergence of these isolates, indicating that pertactin expression is not essential for virulence for B. parapertussis, is discussed.