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Open Access Research article

Comparative genomic profiling of Dutch clinical Bordetella pertussis isolates using DNA microarrays: Identification of genes absent from epidemic strains

Audrey J King1*, Tamara van Gorkom1, Jeroen LA Pennings2, Han GJ van der Heide1, Qiushui He3, Dimitri Diavatopoulos4, Kees Heuvelman1, Marjolein van Gent1, Karin van Leeuwen1 and Frits R Mooi1

Author Affiliations

1 Laboratory for Infectious Diseases and Screening (LIS) Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands

2 Laboratory for Health Protection Research, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands

3 Pertussis Reference Laboratory, National Public Health Institute, Turku, Finland

4 Department of Microbiology and Immunology, University of Melbourne, Victoria, Australia

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BMC Genomics 2008, 9:311  doi:10.1186/1471-2164-9-311

Published: 30 June 2008

Abstract

Background

Whooping cough caused by Bordetella pertussis in humans, is re-emerging in many countries despite vaccination. Several studies have shown that significant shifts have occurred in the B. pertussis population resulting in antigenic divergence between vaccine strains and circulating strains and suggesting pathogen adaptation. In the Netherlands, the resurgence of pertussis is associated with the rise of B. pertussis strains with an altered promoter region for pertussis toxin (ptxP3).

Results

We used Multi-Locus Sequence Typing (MLST), Multiple-Locus Variable Number of Tandem Repeat Analysis (MLVA) and microarray-based comparative genomic hybridization (CGH) to characterize the ptxP3 strains associated with the Dutch epidemic. For CGH analysis, we developed an oligonucleotide (70-mers) microarray consisting of 3,581 oligonucleotides representing 94% of the gene repertoire of the B. pertussis strain Tohama I. Nine different MLST profiles and 38 different MLVA types were found in the period 1993 to 2004. Forty-three Dutch clinical isolates were analyzed with CGH, 98 genes were found to be absent in at least one of the B. pertussis strains tested, these genes were clustered in 8 distinct regions of difference.

Conclusion

The presented MLST, MLVA and CGH-analysis identified distinctive characteristics of ptxP3 B. pertussis strains -the most prominent of which was a genomic deletion removing about 23,000 bp. We propose a model for the emergence of ptxP3 strains.