First report and detailed characterization of B. pertussis isolates not expressing Pertussis Toxin or Pertactin

Bordetella pertussis isolates not expressing Pertussis Toxin (PT) or Pertactin (PRN) have been collected, for the first time in 2007, in France, a highly vaccinated country with acellular vaccines. Non-expression was due to deletion of the entire ptx locus, to IS481 insertion in the prn gene or deletion of a part of this gene. Genome sequencing does not indicate any regions of differences when compared to other circulating isolates. It nevertheless shows some sequence differences and an increased number of repeated sequences. The infant infected by the isolate not expressing pertussis toxin, did not present hyperlymphocytosis. All isolates were found less pathogen in animal or cellular models; their circulation raises the problem of clinical and biological diagnoses.