Occurrence of antibiotic resistance genes in aquatic microbial communities exposed to anthropogenic activities

Résumé

Antibiotic resistance is considered a natural phenomenon since a lot of microorganisms have intrinsic genes that encode resistance to the antibiotics that they produce themselves. However, an increasing number of studies have supported the idea that the overuse and misuse of antimicrobial agents has led to the selection of drug-resistant strains. Besides that, due to the anthropogenic pollution, the natural environment has become a reactor where bacteria from different origins, antibiotics, disinfectants and heavy metals are mixed, contributing to the evolution and spread of antibiotic resistance the environment. Therefore, although most of the research about antibiotic resistance has focused on resistance in clinically relevant human pathogens, it is currently well-known that environmental bacteria play an important role in the emergence and spread of antibiotic resistance genes. In this context, the present thesis aimed to investigate the occurrence of antibiotic resistance genes in aquatic microbial communities influenced by anthropogenic activities. Overall, antibiotic resistance genes were detected in many environments including different matrices (water, biofilm and sediment), different organisms (bacteriophages and bacteria) and different sources (rivers, effluents from several human and veterinary hospitals, subterranean water, chicken faeces and wastewater treatment plant effluents), indicating that these emerging pollutants are widely distributed in the environments exposed to anthropogenic activities. In conclusion, the results obtained in this thesis represent one of the first approaches of antibiotic resistance genes occurrence in our area since most of the studies about antibiotic resistance are still focused on clinical settings.