Effect of vaccination on Bordetella pertussis strains, China

Abstract

Whole-cell pertussis vaccine was introduced in China in the early 1960s. We used standard typing methods to compare 96 Bordetella pertussis isolates collected before and after introduction of vaccination, during 1953-2005. The following vaccine-type alleles of the pertussis toxin (ptx) gene were characteristic for all prevaccination strains: ptxA2, ptxA3, and ptxA4. The shift to ptxA1 occurred since 1963. All isolates collected since 1983 contained ptxA1. Pertactin (prn) allele 1, prn1, was predominant, although prn2 and prn3 have been detected since 2000. Serotypes fimbriae (Fim) 2 and Fim2,3 were found in all isolates collected before 1986. During 1997-2005, Fim3 became prevalent. Although changes in electrophoresis profiles over time were observed, the predominant profiles during 1997-2005 resembled those during the prevaccine era and those found in Europe before the 1990s. B. pertussis strains in China may differ from those in countries that have a long history of high vaccine coverage.

Figure 1

Number of reported pertussis cases and pertussis vaccination coverage in China, 1983–2008 (12). Although vaccination coverage increased with time, it was low before the 1980s and only 58% in 1983.

Figure 2

Frequencies of A) fimbrial (fim) serotypes, B) pertussis toxin (ptx) A alleles, and C) pertactin (prn) alleles in Bordetella pertussis isolates collected in China during 1953–1958, 1963–1985, and 1997–2005.

Figure 3

Dendrogram analysis of 27 pulsed-field gel electrophoresis profiles of Bordetella pertussis isolates circulating in China during 1953–2005. The unweighted pair group method with arithmetic mean with 1% band tolerance and 1% optimization settings was used as the clustering method. * indicates international reference strains (17,23); † indicates vaccine strains from China. Vaccine strains P3s10 and CS represent BpCHR6, and vaccine strain 18530 represents BpFINR13.

Figure A1

Distribution of the Bordetella pertussis isolates collected during 1953–2005 in China. Places where the isolates were recovered are indicated by shading, and the numbers of isolates obtained from each location are provided within parenthesis. Of the 96 isolates studied, no information about origin was available for no. 23.

Figure A2

Amino acid sequence of pertactin (Prn) of Bordetella pertussis from China. Numbering is relative to the first methionine of Prn1. Dots represent identical sequences and dashes represent deletions. The RGD (arg-gly-asp) motif implicated in adherence to host receptors is indicated.