PhD defence by Markus Johansson
On Thursday 11 April Markus Johansson will defend his PhD thesis "The role of mobile genetic elements for the transmission of antimicrobial resistance worldwide"
Supervisors:
- Principal supervisor: Associate Professor Thomas Nordahl Petersen
- Co-supervisor: Professor Frank Møller Aarestrup
Examiners:
- Associate Professor Christian Brinch, DTU Food
- Senior Researcher Henrik Hasman, Statens Serum Institut
- Professor Erik Kristiansson, Department of Mathematical Sciences, Chalmers University of Technology/University of Gothenburg
Chairperson at defence:
- Senior Researcher Rolf Sommer Kaas, DTU Food
Resume
Since the discovery of Penicillin in 1928 have, readily available antibiotics revolutionized modern healthcare and saved countless lives. However, the rapidly increasing number of bacteria resistant to multiple antibiotics poses a significant threat to modern healthcare and global public health.
Bacteria can become antibiotic-resistant by acquiring specific genes, usually through the help of mobile elements. Mobile elements are a group of entities that reside in bacterial cells and can either move between bacteria or within the bacterial DNA. These entities can carry genes and thus help spread them between bacterial populations.
In our first project, we developed a new software for identifying mobile elements in sequenced bacterial genomes. In the following projects, we used this software to determine the mobile elements from different bacterial species and countries.
We found that some mobile elements could be more important for spreading resistance genes. These elements were more frequently associated with several resistance genes. Most of these mobile elements cannot move between bacterial cells alone, suggesting that other mobile elements transport them.
In addition to knowing which mobile elements might be better at transporting resistance, it is also essential to understand how these mobile elements can move between bacteria. Can all mobile elements go everywhere, or are they more prone to move between specific species? We found that most mobile elements exist in a few related species, suggesting that genes carried by these elements have a limited reach. Interestingly, some mobile elements have more potential to spread since they exist in multiple unrelated species. What makes these mobile elements capable of more extensive spread is currently unknown and is subject to future research.
By estimating to which bacteria, the individual mobile elements could spread, we could start eluding the transpositional network that moves genes between bacteria. This could allow us in the future to estimate the risk of a newly discovered antibiotic resistance gene ending up in disease-causing bacteria.