Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2019

Pertactin-Negative and Filamentous Hemagglutinin-Negative Bordetella pertussis, Australia, 2013–2017 (#206)

Zheng Xu 1 , Sophie Octavia 1 , Laurence Don Wai Luu 1 , Michael Payne 1 , Verlaine Timms 2 3 , Alfred Chin Yen Tay 4 , Anthony D Keil 5 , Vitali Sintchenko 2 3 , Nicole Guiso 6 , Ruiting Lan 1
  1. School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia
  2. Centre for Infectious Diseases and Microbiology–Public Health, Institute of Clinical Pathology and Medical Research, Westmead Hospital, New South Wales, Australia
  3. Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Sydney, New South Wales, Australia
  4. Pathology and Laboratory Medicine, University of Western Australia, Perth, Western Australia, Australia
  5. Department of Microbiology, PathWest Laboratory Medicine WA, Perth Children’s Hospital, Perth, Western Australia, Australia
  6. Molecular Prevention and Therapy of Human Diseases, Institut Pasteur, Paris, France

Background: Pertussis (whooping cough) is a vaccine preventable disease caused by the bacterium Bordetella pertussis. Despite high vaccine coverage, pertussis has re-emerged to cause epidemic level disease. Our prior studies have shown a rapid increase in the proportion of B. pertussis isolates not expressing Pertactin (PRN) during the 2008-2012 epidemic. As a new pertussis epidemic occurred in 2015 and to further our understanding of pertussis epidemiology, we genotypically and phenotypically characterised 78 Australian B. pertussis isolates from 2013-2017, and compared their molecular characteristics with isolates from the 2008-2012 epidemic.


Methods: Whole-genome sequencing was performed on 78 clinical isolates collected from 2013-2017 to detect single-nucleotide polymorphisms (SNPs) in virulence genes and to determine their SNP profiles (SP). Together with 27 previously sequenced Australian B. pertussis isolates, a total of 105 isolates were analysed to determine their phylogenetic relationships. Western immunoblotting was performed to detect the expression of the acellular vaccine antigens; pertussis toxin (PTX), PRN and filamentous haemagglutinin (FHA) proteins.


Results: The 78 isolates were typed into two SPs: SP13 (SNP cluster I, ptxP3, 96.15% [75/78]) and SP18 (non-cluster I, ptxP1, 3.85% [3/78]). The majority (75/78, 96.15%) of the SP13 isolates had the prn2 and fim3A allele. Three non-cluster I SP18 isolates were genotyped as ptxP1-fim3A*-prn1. The frequency of ptxP and fim3 alleles were higher than those observed during the last epidemic. For PRN, 89.74% (70/78) of the isolates were found to be PRN-negative. By contrast, the percentage of PRN-negative isolates increased from 5.13% in 2008 to 77.78% in 2012. One novel PRN inactivation mechanism and a novel fim2-3 allele were also found in this study. Importantly, we detected the first FHA-negative B. pertussis isolate in Australia.


Conclusion: The Australian 2013-2017 pertussis epidemic was predominantly caused by PRN-negative isolates, with local and interstate expansion. Our results suggest that B. pertussis continues to evolve under vaccine-induced selective pressure.