Study of the clinical evolution of β-lactamase PDC in a hypermutable linage of Pseudomonas aeruginosa

Congreso; Gordon Research Conference on New Antibacterial Discovery and Development; 2022

Gordon Research Conferences (GRC)

The development of novel therapies to combat antibiotic resistance depends on the knowledge of the different mechanisms of resistance and their evolution upon the currently available therapeutic options. This is the main underlying hypothesis and driving force for my Ph.D. project.In particular, I want to study the evolutionary traits developed in a β-lactamase from the molecular point of view (biochemical and biophysical features) within a clinical context. In order to pursue this ambitious goal, the study system is the chrosomosal serine β-lactamase AmpC from Pseudomonas aeruginosa. The AmpC variants I am currently studying derive from theidentification of resistant alleles from P. aeruginosa isolates from sputum samples of a cystic fibrosis patient who has been treated with β-lactam antibiotics during more than two decades.This allows us to integrate deep sequencing data from the clinical isolates along this long period of time from a single fibrocystic patient and ultimately attempt to correlate the gain-of-function of the mutations accumulating in the ampC gene with the antibiotic therapy through this period. The hypermutability of the colonizing P. aeruginosa strain results in several generations of AmpCmutants, some of them coexisting. This requires the analysis of the resistance phenotype of each variant, the impact of the mutations on the enzyme stability in vitro and in the periplasm, the epistatic effects among the different mutations, and the structural features that enable the most restistant mutants to face the action of newly introduced antibiotics.Based on these premises, I have been able to provide a biochemical and structural rationale accounting for the development of resistance to ceftozolozane in a patient who was never treated with this last generation cephalosporin. This required the integration of multidisciplinaryapproaches and experiments, and I conclude that this may provide the bases to anticipate future resistance events.