Rapid detection of the recently emerged Bordetella pertussis strains with the ptxP3 pertussis toxin promoter allele by real-time PCR.

Bordetella pertussis strains with the pertussis toxin promoter allele ptxP3 have expanded and replaced resident ptxP1 strains in several European countries. We developed an allele-specific real-time PCR method to identify strains with the allele ptxP3, and investigated the emergence of ptxP3 strains by genotyping Finnish clinical isolates (n = 524) from 1953 to 2010. The first ptxP3 strain was detected in 1994, and has become predominant since 2003. Our results demonstrate that the allele-specific real-time PCR is a suitable method for rapid detection of ptxP3 strains, and show the emergence and establishment of ptxP3 strains in Finland.