Resumen de Antibiotic resistance genes in the viral DNA fraction of environmental samples = Gens de resistència a antibiòtics en el DNA de la fracció vírica de mostres ambientals
The PhD thesis presented here has as a main objective the study of antibiotic resistance genes clinically relevant in the DNA fraction of bacteriophage particles isolated from environmental samples of different origin in order to determine the importance of bacteriophages as vehicles for the mobilization of antibiotic resistance genes between bacteria. Specifically, a broad range of antibiotic resistance genes were studied as representative of the main groups recently described in our geographical area belonging to three ?-lactamases (blaTEM, blaCTXM-1 and blaCTX-M-9), the mecA gene conferring resistance to methicillin in staphylococci, and the quinolones resistance genes qnrA and qnrS. To achieve these goals samples of urban wastewater, river water and animal faecal wastes were analysed quantifying the antibiotic resistance genes of interest in bacteriophages DNA. During the development of this Thesis, it was attempted to optimize the available methodology for bacteriophage DNA extraction, as well as the necessary controls to guarantee the amplification of encapsidated DNA and to remove any free DNA in the samples and any possible vesicles containing DNA. In addition, the ability of phage-encoded genes to confer antibiotic resistance in bacterial strains was assessed by performing transformation experiments. It was also studied the influence of various compounds involved in the induction of the lytic cycle of temperate bacteriophages, on the abundance of antibiotic resistance genes in DNA from the phage fraction in wastewater samples. Finally, due to the importance of horizontal gene transfer as a mechanism for antibiotic resistance dissemination in clinical and environmental settings, transduction experiments were attempted to reproduce in vitro the process that would take place in nature. The research developed in this Thesis is divided into 5 studies included in 4 chapters: (1) Antibiotic resistance genes in the bacteriophage DNA fraction of water samples (wastewater, river water and animal wastewater); (2) Quinolone resistance genes (qnrA and qnrS) in bacteriophage particles from wastewater samples and the effect of inducing agents on packaged antibiotic resistance genes; (3) Evaluation of ARGs in the DNA of bacterial and bacteriophage fraction in wastewater samples from Tunisia and comparison with results obtained in Barcelona area; (4) Detection of quinolone-resistant Escherichia coli isolates belonging to clonal groups O25b:H4-B2-ST131 and O25b:H4-D-ST69 in water samples from Barcelona area. Each of the studies has given rise to a scientific article already published or submitted for scientific publication.
