Molecular typing and epidemiology of Bordetella pertussis in Australia

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Pertussis, commonly known as whooping cough, is an acute respiratory disease caused by Bordetella pertussis. Despite more than half a century of vaccination, pertussis has remained endemic in Australia, causing epidemic outbreaks every 3 to 4 years. Indeed the incidence has been increasing in recent years with over 11,000 cases notified in 2005.Pertussis is the commonest of all vaccine preventable diseases targeted by the Australian standard vaccination schedule. To control pertussis, appropriate epidemiological surveillance must be implemented to monitor the circulating B. pertussis strains and emergence of any new strains, in particular those that escape the protection by vaccines. This project will use a novel genomic comparison approach to find variation known as single nucleotide polymorphisms (SNP) present around the genome. We will use these SNPs to analyse a large collection of Australian and worldwide isolates to identify those SNPs most suitable for typing and determine the optimal number of SNPs needed for discrimination. A standardized, consistent and reliable typing method for strain identification will be established. We will further develop an integrated method for detecting known variation in the genes encoding the five acellular vaccine antigens. A combined method for strain identification and detection of antigenic variation will then be developed for culture-independent typing, enabling identification of the strain infecting an individual directly from a clinical sample without the need for culture. This study will establish molecular methods for surveillance of pertussis in Australia, essential for further improvement of acellular pertussis vaccines and public health control measures.