Aeromonas spp.: model for monitoring the impact and diffusion of antibiotic compounds in water environments.

Mauri, Federica (2015) Aeromonas spp.: model for monitoring the impact and diffusion of antibiotic compounds in water environments. PhD thesis, Università Insubria, Varese.

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Antibiotic resistant bacteria and antibiotic resistance genes cause increasing problems in clinical setting and are worldwide considered emerging environmental contaminants, but little is known about their fate in the receiving environment and how natural microbial populations may be affected. In the environment, antibiotic resistant bacteria (e.g. pathogen) may die but their resistance determinants may become part of the environmental gene pool via horizontal gene transfer to environmental bacteria. From this localization, resistance genes may move back to human and animal bacteria via food and drinking water. Natural environment, especially water, is considered a “hot spot” for spread of antibiotics resistance in this scenario Aeromonas spp. were considered the model of hydric microorganisms exposed to the actions of residual antibiotic compounds and to the aquatic resistome, whereas Faecal Coliforms represented the allochthonous population contaminating the aquatic environment. In order to investigate how these two bacterial populations could be influenced by potential antibiotic pollution, we want to examine the presence, the distribution and the transferability of transposons, integrons, and plasmids in Aeromonas spp. and Faecal Coliforms isolated from different aquatic environments submitted to a diverse degree of antibiotic contamination. In this work, we want to highlight if there are common genetic determinants in the two populations and check the potential transferability of these genetic determinants. Conjugation, natural transformation and transduction are the three mechanisms of horizontal antibiotic resistance genes transfer among bacteria. Additionally, we want to investigate if Aeromonas could also be a good donor in mating experiments with other bacteria and if it is able to naturally acquired free DNA from the environment and if Aeromonas DNA could be incorporated by natural competent bacteria. Finally we want to study lytic and lysogenic bacteriophages of Aeromonas spp., investigate the presence of resistance genes on phage DNA and evaluate if phage can transfer these resistance genes by transduction experiments.

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