Skip directly to site content Skip directly to page options Skip directly to A-Z link Skip directly to A-Z link Skip directly to A-Z link
Volume 11, Number 1—January 2005

Bordetella pertussis Isolates, Finland

On This Page
Article Metrics
citations of this article
EID Journal Metrics on Scopus

Cite This Article

To the Editor: Pertussis, or whooping cough, is a highly contagious respiratory disease in humans caused by Bordetella pertussis. Reemergence of pertussis has been observed in many countries with high vaccination coverage. In the United States, reported cases of pertussis in adolescents and adults have increased since the 1980s, despite increasingly high rates of vaccination in infants and children (1). At the same time, clinical B. pertussis isolates have become antigenically divergent from vaccine strains (2,3). This observation has raised the question of whether vaccination has caused selection for the variant strains, and whether the reemergence of pertussis in vaccinated populations is due to vaccination not protecting against these antigenic variants as effectively as it protects against vaccine type strains. On the other hand, vaccine-induced immunity wanes over time, and pertussis is not only a childhood disease but also a frequent cause of prolonged illness in adults and adolescents today (4).

In Finland, children are vaccinated with diphtheria-tetanus whole-cell pertussis vaccine at 3, 4, and 5 months, and at 20 to 24 months of age. The whole-cell vaccine contains 2 strains and has remained unchanged since 1976. The vaccine strain 18530 contains fimbriae 3 (Fim3), pertussis toxin S1 subunit D (PtxS1D), and pertactin 1(Prn1); the other vaccine strain, 1772, contains Fim2,3, PtxS1B, and Prn1. Ninety-six percent of Finland's population has been vaccinated with 4 doses of pertussis vaccine. The incidence of pertussis is highest in infants <1 year of age and in schoolchildren from 6 to 14 years old, although about 30% of the cases occur in adults older than 20 years. In Finland, as in many other countries with large-scale vaccination programs, several outbreaks of pertussis occurred in the 1990s. We studied prospectively 3 pertussis outbreaks in 2 elementary schools and 1 municipality in southwestern Finland (5,6). The aim of the study was to characterize the strains circulating and causing outbreaks and to track the transmission of B. pertussis during these outbreaks.

Sample were collected and primary cultures were done as described earlier (5,6). The outbreaks took place in 3 rural municipalities: in 1992, in Paimio (Table 1) with 9,900 inhabitants; in 1995, in Oripää (Table 2) with 1,400 inhabitants; and in 1996, in Rusko (Table 3) with 3,500 inhabitants. The isolates were obtained from schools and local health centers. In addition, 1 isolate was obtained from a household contact (Table 3). Most of the cases occurred in schoolchildren >8 years of age and in adults.

Various DNA fingerprinting techniques, such as IS1002-based restriction fragment length polymorphism (IS1002-RFLP) and pulsed-field gel electrophoresis (PFGE) have been used to study B. pertussis isolates (710). DNA polymorphism analysis of prn and ptxS1 has previously been used as a typing method for detecting antigenic shifts (2,3,8). In addition to prn and ptxS1, only tracheal colonization factor (tcfA), a surface–associated protein involved in the adhesion of B. pertussis to host cells, has been found to be polymorphic in recent B. pertussis isolates (3). The isolates were typed as described earlier (8,10).

Of the 46 isolates, 43 (94%) expressed Fim2, 2 (4%) expressed both Fim2 and Fim3, and 1 (2%) expressed Fim3 (Tables 1, 2 and 3). The predominant prn allele in all 3 outbreaks was prn2, contained by 39 (85%) of the isolates. Six (13%) isolates contained prn3 and 1 (2%) isolate contained prn4. All isolates contained the ptxS1A allele. The predominant tcfA allele was tcfA2, contained by 42 (91%) of the isolates. Four (9%) isolates contained tcfA3. The tcfA3 allele was observed only in isolates with prn3. All but 1 of the 27 isolates subjected to the IS1002-RFLP analysis had the same pattern.

Seven PFGE patterns were found among the 46 isolates studied. The isolates were considered to be closely related, as the differences between the patterns were small, differing by 1 or 2 bands. Three PFGE patterns were found in both Paimio and Rusko. A major pattern was circulating in each of the schools A, B, and C, which indicates that pertussis is effectively transmitted in schools. However, in school D, the isolate from the index patient had PFGE pattern 5, whereas the rest of the isolates from patients in school D had pattern 6. In addition, the 1 isolate obtained from a household contact had a distinct PFGE pattern, 7. Similarly, in Paimio, the isolate from the index patient had a distinct PFGE pattern, 1. These findings, as well as the fact that 3 PFGE patterns were found in both Paimio and Rusko, indicate that several B. pertussis strains may have been circulating simultaneously in these small communities.

Our results suggest that ptxS1 is not a useful marker in outbreaks to detect antigenic shifts. IS1002-RFLP was less discriminative than XbaI PFGE, which agree with results of previous studies (8). Most cases occurred in schoolchildren and adults, confirming epidemiologic findings from other countries with vaccination programs. Our results support the earlier observation that the recent B. pertussis isolates are antigenically different from vaccine strains. Several B. pertussis strains could circulate simultaneously even in small communities, and only some strains, possibly with increased fitness, are capable of spreading effectively.



We thank Anna Musku and Birgitta Aittanen for technical assistance.

The Academy of Finland, the Special Governmental Fund for University Hospitals (EVO), and the European Commission Quality of Life Program (QLK2-CT-2001-01819) financially supported this work.


Johanna Mäkinen*†Comments to Author , Jussi Mertsola‡, Frits R. Mooi§, Shirley Van Amersfoorth‡, Heikki Arvilommi*, Matti K. Viljanen‡, and Qiushui He*
Author affiliations: *National Public Health Institute, Turku, Finland; †Turku Graduate School of Biomedical Sciences, Turku, Finland; ‡University of Turku, Turku, Finland; §National Institute of Public Health and the Environment, Bilthoven, the Netherlands



  1. Tanaka  M, Vitek  CR, Pascual  FB, Bisgard  KM, Tate  JE, Murphy  TV. Trends in pertussis among infants in the United States, 1980–1999. JAMA. 2003;290:296875. DOIPubMedGoogle Scholar
  2. Mooi  FR, He  Q, van Oirschot  H, Mertsola  J. Variation in the Bordetella pertussis virulence factors pertussis toxin and pertactin in vaccine strains and clinical isolates in Finland. Infect Immun. 1999;67:31334.PubMedGoogle Scholar
  3. van Loo  IH, Heuvelman  KJ, King  AJ, Mooi  F. Multilocus sequence typing of Bordetella pertussis based on surface protein genes. J Clin Microbiol. 2002;40:19942001. DOIPubMedGoogle Scholar
  4. von Konig  CH, Halperin  S, Riffelmann  M, Guiso  N. Pertussis of adults and infants. Lancet Infect Dis. 2002;2:74450. DOIPubMedGoogle Scholar
  5. Tran Minh  NN, He  Q, Edelman  K, Olander  R-M, Viljanen  MK, Arvilommi  H, Cell-mediated immune responses to antigens of Bordetella pertussis and protection against pertussis in school children. Pediatr Infect Dis J. 1999;18:36670. DOIPubMedGoogle Scholar
  6. He  Q, Viljanen  MK, Ölander  R-M, Bogaerts  H, De Grave  D, Ruuskanen  O, Antibodies to filamentous hemagglutinin of Bordetella pertussis and protection against whooping cough in school children. J Infect Dis. 1994;170:7058. DOIPubMedGoogle Scholar
  7. van der Zee  A, Vernooij  S, Peeters  M, van Embden  J, Mooi  FR. Dynamics of the population structure of Bordetella pertussis as measured by IS1002-associated RFLP: comparison of pre- and post- vaccination strains and global distribution. Microbiology. 1996;142:347985. DOIPubMedGoogle Scholar
  8. Mooi  FR, Hallander  H, von Konig  CH, Hoet  B, Guiso  N. Epidemiological typing of Bordetella pertussis isolates: recommendations for a standard methodology. Eur J Clin Microbiol Infect Dis. 2000;19:17481. DOIPubMedGoogle Scholar
  9. de Moissac  YR, Ronald  SL, Peppler  MS. Use of pulsed-field gel electrophoresis for epidemiological study of Bordetella pertussis in a whooping cough outbreak. J Clin Microbiol. 1994;32:398402.PubMedGoogle Scholar
  10. Mäkinen  J, Mertsola  J, Soini  H, Arvilommi  H, Viljanen  MK, Guiso  N, PFGE and pertactin gene sequencing suggest limited genetic variability within the Finnish Bordetella parapertussis population. J Med Microbiol. 2003;52:105963. DOIPubMedGoogle Scholar




Cite This Article

DOI: 10.3201/eid1101.040632

Related Links


Table of Contents – Volume 11, Number 1—January 2005

EID Search Options
presentation_01 Advanced Article Search – Search articles by author and/or keyword.
presentation_01 Articles by Country Search – Search articles by the topic country.
presentation_01 Article Type Search – Search articles by article type and issue.



Please use the form below to submit correspondence to the authors or contact them at the following address:

Johanna Mäkinen, Mycobacterial Reference Laboratory, National Public Health Institute, Kiinamyllynkatu 13, 20520 Turku, Finland; fax: 358-2-331-6699

Send To

10000 character(s) remaining.


Page created: April 25, 2012
Page updated: April 25, 2012
Page reviewed: April 25, 2012
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.