André, S., Novo, A., Nunes, O. C., Manaia, C. M., & Viana, P. (2013). Antibiotic resistance, antimicrobial residues and bacterial community composition in urban wastewater. Water Research. 47 (5), 1875–1887.

The authors of this publication, individually affiliated with the either the Catholic University of Portugal, the Portuguese Environment Agency, or the University of Porto, addressed the question of whether abiotic factors and wastewater treatment played roles in the levels of antibiotic resistance or varied bacterial community structures on the microbes in the effluent water.  This was achieved by collecting samples of both treated and untreated water throughout several different windows of time between two years and using methods such as specialized forms of gel electrophoresis to identify characteristics of the microorganisms captured, along with forms of spectroscopy and chromatography among several other analytical methods to identify other pollutants. The results demonstrated that concentrations of antibiotic contaminants being present in the raw wastewater correlated with the composition of the bacteria evaluated in the treated water. Temperature and the organic load present in the water appeared to be the strongest abiotic factors that contributed to impacting the composition of the bacterial communities evaluated and may potentially have been a result of the quality of the raw water as opposed to a byproduct of the treatment itself. A gap identified by the study was that identifying whether antibiotic presence in the water was the major contributor to variations in the bacteria is difficult to find evidence for due to it being hard to isolate from other contributing factors that may also be influencing the bacterial community. This article was similar to that of Burch et al in terms of the similar objectives each study had, either of them pertaining heavily to antibiotic resistant genes in relation to water treatment. This article relates to my Capstone topic in that it identifies one factor believed to be a large influence on the presence of antibiotic resistant bacteria in the environment and presents methods of analysis that may be used in determining so.

Arabi, M., Pruden, A., & Storteboom, H. N. (2012). Correlation between upstream human activities and riverine antibiotic resistance genes. Environmental Science & Technology, 46 (21), 11541–11549.

The authors of this article, affiliated with Virginia Tech and/or Colorado State University, investigated the correlation between antibiotic resistant genes and human activity near or along waterways. The method of evaluating this question was the collection of water samples along the South Platte River Basin, including rivers originating from pristine water sourced from the Rocky Mountains and traveling through multiple areas of human activity, including facilities where animals are fed, plants treating contaminated water, and areas containing fish hatchery and rearing units. The results determined that there were strong correlations between sulfonamide measurements generally increasingly significantly as the water shifted from the pristine regions to areas more impacted by human activity. The animal feeding areas appeared the be the larger contributor of the antibiotic. Tetracycline did not appear to have as strong of a correlation with human activity and was dispersed throughout the region. A next step the study identified was developing a standardized method for accounting for and listing human-related sources of antibiotic resistant genes. This work was similar to that of Burch et al due to its evaluation of pristine and relatively disrupted water sources in comparison to one another. This work relates to my Capstone topic because of it detailing methods of water and sediment analysis that could be applied to samples we collect to answer similar questions as those posed by this article.

Baker-Austin, C., Maskell, D. J., Micallef, C., Pearce, G. P, Rowe, W. P., Ryan, J. J., & Verner-Jeffreys, D. W. (2017). Overexpression of antibiotic resistance genes in hospital effluents over time. Journal of Antimicrobial Chemotherapy, 72 (6), 1617–1623. 

The authors of this article, individually associated or affiliated with the Centre for Environment, GlaxoSmithKline, Addenbrooke’s and Cambridge University Hospitals, or the University of Cambridge, sought to evaluate whether treated water sourced from areas of antibiotic usage had an impact on the aquatic areas receiving the effluent. The researchers accomplished this by collecting samples from treated water that had originated from both a hospital and a dairy farm and comparing the effluents of either of these to the River Cam which would be receiving both effluents. The results determined that the effluent of the hospital wastewater contained more antibiotic resistance genes than that of the farm and exponentially more than the river source water. This allowed for the conclusion to be made that effluents previously exposed to higher concentrations of antibiotic residue and/or contaminants results contain a significant amount of antibiotic resistance genes. A gap or area of note that the article touched on was one of the forms of sample evaluation, metatranscriptomic analysis, having the potential to be impacted by variables that may lead to certain genes being represented more or less, the example provided being transcript half-life. This article’s findings were similar to that of Arabi & Sorteboom in terms of determining there being a correlation between high antibiotic concentration in effluent sourced from antibiotic containing untreated water. This article informs my Capstone topic due to it providing examples of what kinds of factors may  have the largest impact on the presence of antibiotic resistance genes in environmental microbes.

Burch, T. R., Eichmiller, J. J., LaPara, T. M., McNamara, P. J., Tan, D. T., & Yan, M. (2011). Tertiary-treated municipal wastewater is a significant point source of antibiotic resistance genes into Duluth-Superior Harbor. Environmental Science & Technology, 45 (22), 9543–9549.

The researchers who contributed to this work, affiliated with the University of Minnesota, sought to address the question of whether tertiary-treated wastewater had an impact on the presence of antibiotic resistance determinants through sample collection at the Duluth-Superior Harbor. Samples of water and sediment were collected from a series of locations along the St. Louis River, Duluth-Superior Harbor, and Lake Superior. These particular water locations were of interest due to the St. Louis River and Lake Superior being considered relatively pristine in comparison to the harbor which is located most proximally to the treated water from the area that was observed in the Western Lake Superior Sanitary District. The study found that amounts of  antibiotic resistant genes were on average 20-fold more in the treated water than those found in neighboring surface waters, a substantial difference when compared to the antibiotic resistant gene content of Lake Superior and the St. Louis river which generally fell below detection quantities. This resulted in the conclusion being drawn that water treatment facilities have a significant impact on the presence of antibiotic resistant genes in aquatic environments. A gap in this study may be that at the time of its publication, the authors stated that it was unique in that it was able to distinguish tertiary wastewater treatment as a cause of antibiotic resistance. Further research in this area with the same kinds of facilities may strengthen or expand upon their findings. This article was different in terms of its findings to the treated water observed by André et al in that the results for that study presented correlations that were not as strongly tied to the facility’s treatment and more related to environmental factors. This article’s contents would be able to inform my Capstone due to its evaluation of several different water quality types in relation to antibiotic resistance.

Fick, J., Larson, J. D. G., Lindberg, R. H., Phan, C., Söderström, H., & Tysklind, M. (2009). Contamination of surface, ground, and drinking water from pharmaceutical production. Environmental Toxicology and Chemistry, 28 (12), 2522–2527.

The authors of this work, researchers at Umeå University and University of Gothenburg, aimed to investigate how significant an impact the bulk production of pharmaceuticals posed on the water sources of the surrounding environments. They were able to achieve this through analyzing samples from an effluent treatment plant in Hyderabad, India that collects and treats water from an estimated 90 bulk pharmaceutical manufacturers. Their samples were collected from areas surrounding the treatment plant itself, water from the treated stream, two lakes removed from the plant’s incoming or outgoing stream, and wells in several neighboring villages. The wells were found to be contaminated with the pharmaceuticals, and high antibiotic concentrations were found in both the treatment plant’s effluent and the evaluated lakes. This seemed to back the theory that the management of untreated water is a significant contributor to environmental exposure to antibiotic substances. A next step the article identified was potentially evaluating the risks pharmaceutical contaminated waters may pose to human health, such as during formative years or towards pregnancy. The findings of this work were comparable to those made by Baker-Austin et. al. in relation to evaluating treated water from facilities with higher antibiotic usage, in that case being a hospital. This study relates to my Capstone topic in that it provides information about a potential source or influencing factor in antibiotic resistant bacteria found in the environment.