Strain variation among Bordetella pertussis isolates circulating in Poland after 50 years of whole-cell pertussis vaccine use

Abstract

In the present study, clinical isolates of Bordetella pertussis collected in Poland from 1960 to 2005 were analyzed by pulsed-field gel electrophoresis (PFGE) according to protocols recommended in previous studies. Among the 110 isolates from 1995 to 2005, 59 PFGE patterns were found, most of which were different from those currently circulating in other European Union (EU) countries for which data are available. The PFGE patterns of currently disseminating B. pertussis clones were found within PFGE groups III and IV, as elsewhere in the EU, and in newly identified clusters A and C. Up to 70, 26, and 4%, respectively, of the currently isolated strains in Poland harbored ptxA1-prn1, ptxA1-prn2, and ptxA1-prn3 allele combinations, and most (82%) were found to be of the Fim2 phenotype. Differences in the extent of heterogeneity estimated by PFGE typing in B. pertussis populations circulating in Poland in comparison to other EU countries may be due to the different vaccine composition strategy, since routine pertussis vaccination was initiated in Poland in 1960.

Fig. 1.

Dendrogram of 148 B. pertussis strains circulating in Poland from 1960 to 2005. Current vaccine strains are underlined, historical vaccine strains are indicated by an asterisk (*), and reference strains for different PFGE groups are indicated by a dot (●). The groups and clusters were identified to have an overall relatedness of ca. 86%. The classification of the pertactin allele (prn1, prn2, and prn3) and subunit A of the pertussis toxin allele (ptxA1, ptxA2, ptxA3, and ptxA4) is shown.