Dr Siouxsie Wiles

“What makes a microbe infectious?”

Hosted by Professor Shiranee Sriskandan and Dr Brian Robertson

COVID-19 has crystallised the importance of a fundamental question in infectious diseases research: what makes a microbe infectious? This question has proven difficult to answer experimentally, as many experimental disease models do not include natural transmission as a parameter. Whereas we humans can be infected by eating contaminated food, or by contact with a contaminated environment, laboratory animals are almost always infected by being injected with large doses of bacteria grown in rich media. To address this major gap, we have used mice to experimentally investigate the transmission of an infectious gut bacterium – Citrobacter rodentium. In our experiments we asked: does the bacterium evolve to become more or less infectious, and what are the genetic mechanisms that underlie such phenomena? Just as we are seeing variants that increase transmissibility of the SARS-CoV-2 virus, in 8 out of 10 independent transmission chains, C. rodentium became more infectious. I’ll discuss what we know about these strains so far, and the unexpected application this work had to the COVID-19 pandemic. 

 Siouxsie studied medical microbiology at the University of Edinburgh, followed by a PhD in environmental microbiology at the Centre for Ecology and Hydrology in Oxford and Edinburgh Napier University. She spent several years at Imperial where her postdoctoral work on Citrobacter rodentium won the inaugural National Centre for the Replacement, Refinement and Reduction of Animals in Research prize. In 2009, Siouxsie was awarded a Sir Charles Hercus Fellowship from the Health Research Council of New Zealand and relocated to the University of Auckland where she is an Associate Professor. Siouxsie has a keen interest in demystifying science for the public and has won many accolades for her efforts, including the New Zealand Prime Minister’s Science Communication Prize in 2013. Just ten years after arriving in the country, in 2019 Siouxsie was made a member of the New Zealand Order of Merit for services to microbiology and science communication. She became a household name in New Zealand for her COVID-19 communication work, finding herself on the BBC’s list of their 100 influential women of 2020 and being awarded New Zealander of the Year in 2021.

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