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Antibiotic resistance occurs when bacteria evolve to resist the effects of the drugs we use to treat bacterial infections. This global health threat endangers a century of medical progress, leading to longer illness, increased mortality rates, and higher healthcare costs. In her research, Ilmur Jonsdottir dives into AMR and plasmid dynamics, examining clinical gut isolates and the microbiomes of patients. She investigates how conjugative plasmids, bacterial genetic elements which can transfer genes between bacteria, help susceptible neighboring bacteria survive in the presence of antibiotics. Ilmur also explores how ecological and environmental factors impact targeted solutions, like phage therapy and CRISPR antimicrobials, in the fight against antibiotic resistant bacteria.

Antibiotics have temporary impact on gut microbiome

Ilmur conducted an in-depth longitudinal study of the gut microbiome and E. coli isolates from a patient treated with antibiotics to treat uncomplicated acute appendicitis.

“The study revealed that antibiotic treatment impacted gut microbial composition, plasmid dynamics, and favored a certain resistance profile during therapy. However, within six months post-treatment, there was a partial recovery, suggesting the antibiotic's effects were temporary”, says Ilmur Jonsdottir from Ģ��ֱ��

Promiscuous genetic element can mean survival for bacteria

Plasmids, genetic elements in bacteria, often carry genes that provide antibiotic resistance. These plasmids can persist within bacterial communities and transfer between bacteria. Ilmur's research focused on experimentally coevolving plasmids in different bacterial host environments to test their potential to rescue antibiotic susceptible neighbors via transferring resistance genes which otherwise would lead to extinction due to antibiotic exposure (evolutionary rescue). Ilmur discovered that coevolution with specific bacteria created plasmids with host-specific rescue potentials.

Success of targeted solutions against antibiotic resistance relies on greater ecological and evolutionary understanding

In the fight against antibiotic resistance, researchers are exploring innovative solutions like using bacteriophages—viruses that exclusively target bacteria—and CRISPR antimicrobials to remove resistance genes.

“My research delved into environmental factors, such as mucin and antibiotics, that might influence the development of phage resistance—a major challenge for the success of phage therapy”, Ilmur Jonsdottir explains.

Her findings indicated that phage resistance in E. coli and K. pneumoniae was not significantly affected by these environmental factors, but rather depended on the specific phage-host pairings.

Ilmur also contributed to a study on the effectiveness and evolutionary consequences of CRISPR-based antimicrobials. The study revealed that the genetic background of the resistance gene, such as being plasmid-encoded, significantly impacted the success of CRISPR antimicrobials. Additionally, it was observed that plasmids carrying resistance genes were evolving to resist CRISPR targeting, highlighting the dynamic and adaptive nature of bacterial resistance mechanisms.

The examination of M.Sc. Ilmur Jonsdottir’s doctoral thesis “Evolutionary trajectories of conjugative resistance plasmids and their interplay in the ecology of clinically relevant bacteria” is held on Friday 09.08.2024 at 12:00 at Agora in room AgB105 Agora Auditorio 2. The opponent is Lecturer Dr. Ellie Harrison (University of Sheffield, U.K.) and Custos Academy Research Fellow Reetta Penttinen (Ģ��ֱ��). The doctoral dissertation is held in English. 

The dissertation “Evolutionary trajectories of conjugative resistance plasmids and their interplay in the ecology of clinically relevant bacteria” can be read on the JYX publication archive: .