Quantitative characterisation of bacterial regrowth after combinatorial treatment

November 25, 2025

Antimicrobial resistance is a major public health challenge of the 21st century, demanding innovative approaches to evaluate and optimise antibiotic therapies like combination therapies. This thesis aims to validate the Time of Regrowth (TRG) as a quantitative and scalable metric to characterise bacterial survival following combinatorial antibiotic treatments. Escherichia coli and Salmonella Typhimurium were used as model organisms. Results showed a strong agreement of TRG-based synergistic, antagonistic, and neutral interactions with those measured by colony-forming unit (CFU), typically used to quantify bacterial viability. Nonetheless, beyond capturing bacterial viability, TRG also proved sensitive to stress-mediated regrowth delays, providing complementary information to conventional methods. The methodology displayed high reproducibility and consistency, validating TRG as a robust metric for analysing antibiotic interactions. Overall, TRG constitutes a practical and informative approach for evaluating bacterial responses to antibiotic combinations, offering significant advantages for large scale screening. Its integration with quantitative interaction models may support the rational design of combinatorial therapies, contributing to more effective strategies to tackle antimicrobial resistance.

Authors in the community:

• 

  C

  Catarina Fernandes Ferreira

  ist199591

Supervisors of this institution:

• 

  M

  Miguel Nobre Parreira Cacho Teixeira

  ist141827

industrial-biotechnology - Industrial Biotechnology

eng - English

Instituto Superior Técnico