Trends in Microbiology
Volume 22, Issue 1, January 2014, Pages 36-41
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Review
The role of aquatic ecosystems as reservoirs of antibiotic resistance

https://doi.org/10.1016/j.tim.2013.11.001Get rights and content

Highlights

  • Anthropogenic activities may contribute to the spread of antibiotic resistance genes (ARGs) in the environment.

  • Aquatic environments provide ideal settings for the horizontal exchange of mobile genetic elements (MGEs).

Although antibiotic resistance has become a major threat to human health worldwide, this phenomenon has been largely overlooked in studies in environmental settings. Aquatic environments may provide an ideal setting for the acquisition and dissemination of antibiotic resistance, because they are frequently impacted by anthropogenic activities. This review focuses primarily on the emergence and dissemination of antibiotic resistance in the aquatic environment, with a special emphasis on the role of antibiotic resistance genes.

Section snippets

Antibiotic resistance: emergence and impact

The development of antibiotics has been one of the major achievements of the 20th century and millions of human lives have been saved since the 1940s when the first antibiotics, penicillin and streptomycin, were introduced. Antibiotics are used to treat a wide range of bacterial infections and are indispensable in medical treatment such as intensive care, organ transplantation, chemotherapy, care of preterm babies, and surgical procedures, which could not be performed effectively without the

Link between clinical and environmental resistance

Several studies suggest that antibiotic resistance occurs in nature and has an ancient origin, which is not linked to the anthropogenic use of antibiotics 13, 14. In the environment, bacteria have developed an ability to synthesize bioactive molecules to either cooperate with or antagonize other members of the community and, as a result, they have developed defense systems to protect themselves against the molecules of others. These molecules are encoded by genetic elements which constitute the

Acquisition and dissemination of ARGs

Several studies have demonstrated that ARGs are spread by MGEs, including plasmids, insertion sequences, insertion sequence common region elements, transposons, integrons, genomic islands, integrating conjugative elements, and bacteriophages (Table 1, 32, 33, 34, 35, 36, 37, 38), which are involved in bacterial acquisition and recombination of foreign DNA [39]. Plasmids, circular double-stranded DNA molecules that replicate independently from chromosomal DNA, may encode a wide variety of

Aquatic environments as reservoirs of ARGs

It is now clearer than ever that antibiotics act as promoters of antibiotic resistance, and thus may contribute to the acquisition of MGEs [49]. As mentioned above, a diverse mixture of antibiotics and other pollutants, their metabolites and resistant bacteria, reaches the aquatic environment through treated and untreated sewage, hospital waste, aquaculture discharges, and agricultural runoff (Figure 1). These aquatic compartments, such as water and sediment, may therefore have a significant

Concluding remarks

With the increasing use and accessibility to culture-independent techniques that allow the functional and structural characterization of microbial communities, the exploration of ARGs may extend to a wide range of organisms, including uncultured species. These advances will increase our understanding of the evolutionary pathways through which the MGEs encoding ARGs spread within a community. Taking into consideration that ARGs are ‘easy to get, hard to lose’ pollutants and that they may be

Acknowledgments

This study was supported by the Fundación Eugenio Rodríguez Pascual, Spain. E.V. acknowledges the Leonardo da Vinci fellowship (2012-1-GR1 LEO02-09765) from the European Union. J.L.B. acknowledges the Ramon y Cajal research fellowship (RYC-2011-08154) from the Spanish Ministry of Economy and Competitiveness.

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