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Marutescu LG, Popa M, Gheorghe-Barbu I, Barbu IC, Rodríguez-Molina D, Berglund F, Blaak H, Flach CF, Kemper MA, Spießberger B, Wengenroth L, Larsson DGJ, Nowak D, Radon K, de Roda Husman AM, Wieser A, Schmitt H, Pircalabioru Gradisteanu G, Vrancianu CO, Chifiriuc MC. Wastewater treatment plants, an "escape gate" for ESCAPE pathogens. Front Microbiol 2023; 14:1193907. [PMID: 37293232 PMCID: PMC10244645 DOI: 10.3389/fmicb.2023.1193907] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Accepted: 05/09/2023] [Indexed: 06/10/2023] Open
Abstract
Antibiotics are an essential tool of modern medicine, contributing to significantly decreasing mortality and morbidity rates from infectious diseases. However, persistent misuse of these drugs has accelerated the evolution of antibiotic resistance, negatively impacting clinical practice. The environment contributes to both the evolution and transmission of resistance. From all anthropically polluted aquatic environments, wastewater treatment plants (WWTPs) are probably the main reservoirs of resistant pathogens. They should be regarded as critical control points for preventing or reducing the release of antibiotics, antibiotic-resistant bacteria (ARB), and antibiotic-resistance genes (ARGs) into the natural environment. This review focuses on the fate of the pathogens Enterococcus faecium, Staphylococcus aureus, Clostridium difficile, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacteriaceae spp. (ESCAPE) in WWTPs. All ESCAPE pathogen species, including high-risk clones and resistance determinants to last-resort antibiotics such as carbapenems, colistin, and multi-drug resistance platforms, were detected in wastewater. The whole genome sequencing studies demonstrate the clonal relationships and dissemination of Gram-negative ESCAPE species into the wastewater via hospital effluents and the enrichment of virulence and resistance determinants of S. aureus and enterococci in WWTPs. Therefore, the efficiency of different wastewater treatment processes regarding the removal of clinically relevant ARB species and ARGs, as well as the influence of water quality factors on their performance, should be explored and monitored, along with the development of more effective treatments and appropriate indicators (ESCAPE bacteria and/or ARGs). This knowledge will allow the development of quality standards for point sources and effluents to consolidate the WWTP barrier role against the environmental and public health AR threats.
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Affiliation(s)
- Luminita Gabriela Marutescu
- Department of Microbiology and Immunology, Faculty of Biology, Research Institute of the University of Bucharest, University of Bucharest, Bucharest, Romania
- Earth, Environmental and Life Sciences Section, Research Institute of the University of Bucharest, University of Bucharest, Bucharest, Romania
| | - Marcela Popa
- Earth, Environmental and Life Sciences Section, Research Institute of the University of Bucharest, University of Bucharest, Bucharest, Romania
| | - Irina Gheorghe-Barbu
- Department of Microbiology and Immunology, Faculty of Biology, Research Institute of the University of Bucharest, University of Bucharest, Bucharest, Romania
- Earth, Environmental and Life Sciences Section, Research Institute of the University of Bucharest, University of Bucharest, Bucharest, Romania
| | - Ilda Czobor Barbu
- Department of Microbiology and Immunology, Faculty of Biology, Research Institute of the University of Bucharest, University of Bucharest, Bucharest, Romania
- Earth, Environmental and Life Sciences Section, Research Institute of the University of Bucharest, University of Bucharest, Bucharest, Romania
| | - Daloha Rodríguez-Molina
- Institute and Clinic for Occupational, Social and Environmental Medicine, University Hospital, LMU Munich, Munich, Germany
- Institute for Medical Information Processing, Biometry, and Epidemiology – IBE, LMU Munich, Munich, Germany
- Pettenkofer School of Public Health, Munich, Germany
| | - Fanny Berglund
- Department of Infectious Diseases, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
- Centre for Antibiotic Resistance Research in Gothenburg (CARe), University of Gothenburg, Gothenburg, Sweden
| | - Hetty Blaak
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, Netherlands
| | - Carl-Fredrik Flach
- Department of Infectious Diseases, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
- Centre for Antibiotic Resistance Research in Gothenburg (CARe), University of Gothenburg, Gothenburg, Sweden
| | - Merel Aurora Kemper
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, Netherlands
| | - Beate Spießberger
- German Centre for Infection Research (DZIF), Partner Site Munich, Munich, Germany
- Max von Pettenkofer Institute, Faculty of Medicine, LMU Munich, Munich, Germany
- Department of Infectious Diseases and Tropical Medicine, LMU University Hospital Munich, Munich, Germany
| | - Laura Wengenroth
- Institute and Clinic for Occupational, Social and Environmental Medicine, University Hospital, LMU Munich, Munich, Germany
| | - D. G. Joakim Larsson
- Department of Infectious Diseases, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
- Centre for Antibiotic Resistance Research in Gothenburg (CARe), University of Gothenburg, Gothenburg, Sweden
| | - Dennis Nowak
- Institute and Clinic for Occupational, Social and Environmental Medicine, University Hospital, LMU Munich, Munich, Germany
- Comprehensive Pneumology Center Munich (CPC-M), German Center for Lung Research (DZL), Munich, Germany
| | - Katja Radon
- Institute and Clinic for Occupational, Social and Environmental Medicine, University Hospital, LMU Munich, Munich, Germany
| | - Ana Maria de Roda Husman
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, Netherlands
| | - Andreas Wieser
- German Centre for Infection Research (DZIF), Partner Site Munich, Munich, Germany
- Max von Pettenkofer Institute, Faculty of Medicine, LMU Munich, Munich, Germany
- Department of Infectious Diseases and Tropical Medicine, LMU University Hospital Munich, Munich, Germany
| | - Heike Schmitt
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, Netherlands
| | - Gratiela Pircalabioru Gradisteanu
- Department of Microbiology and Immunology, Faculty of Biology, Research Institute of the University of Bucharest, University of Bucharest, Bucharest, Romania
- Earth, Environmental and Life Sciences Section, Research Institute of the University of Bucharest, University of Bucharest, Bucharest, Romania
- Romanian Academy of Sciences, Bucharest, Romania
| | - Corneliu Ovidiu Vrancianu
- Department of Microbiology and Immunology, Faculty of Biology, Research Institute of the University of Bucharest, University of Bucharest, Bucharest, Romania
| | - Mariana Carmen Chifiriuc
- Department of Microbiology and Immunology, Faculty of Biology, Research Institute of the University of Bucharest, University of Bucharest, Bucharest, Romania
- Earth, Environmental and Life Sciences Section, Research Institute of the University of Bucharest, University of Bucharest, Bucharest, Romania
- The Romanian Academy, Bucharest, Romania
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2
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Esser M, Hoggarth C, Baulch H, Challis JK, Xie Y, Giesy JP, Hecker M, Brinkmann M. Wastewater discharges alter microbial community composition in surface waters of the canadian prairies. CHEMOSPHERE 2023; 334:138991. [PMID: 37209843 DOI: 10.1016/j.chemosphere.2023.138991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 05/17/2023] [Accepted: 05/18/2023] [Indexed: 05/22/2023]
Abstract
Microbial communities are an important component of freshwater biodiversity that is threatened by anthropogenic impacts. Wastewater discharges pose a particular concern by being major sources of anthropogenic contaminants and microorganisms that may influence the composition of natural microbial communities. Nevertheless, the effects of wastewater treatment plant (WWTP) effluents on microbial communities remain largely unexplored. In this study, the effects of wastewater discharges on microbial communities from five different WWTPs in Southern Saskatchewan were investigated using rRNA gene metabarcoding. In parallel, nutrient levels and the presence of environmentally relevant organic pollutants were analyzed. Higher nutrient loads and pollutant concentrations resulted in significant changes in microbial community composition. The greatest changes were observed in Wascana Creek (Regina), which was found to be heavily polluted by wastewater discharges. Several taxa occurred in greater relative abundance in the wastewater-influenced stream segments, indicating anthropogenic pollution and eutrophication, especially taxa belonging to Proteobacteria, Bacteroidota, and Chlorophyta. Strong decreases were measured within the taxa Ciliphora, Diatomea, Dinoflagellata, Nematozoa, Ochrophyta, Protalveolata, and Rotifera. Across all sample types, a significant decline in sulfur bacteria was measured, implying changes in functional biodiversity. In addition, downstream of the Regina WWTP, an increase in cyanotoxins was detected which was correlated with a significant change in cyanobacterial community composition. Overall, these data suggest a causal relationship between anthropogenic pollution and changes in microbial communities, possibly reflecting an impairment of ecosystem health.
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Affiliation(s)
- Milena Esser
- Toxicology Centre, University of Saskatchewan, 44 Campus Dr, Saskatoon, SK S7N 5B3, Canada
| | - Cameron Hoggarth
- Global Institute for Water Security, University of Saskatchewan, Innovation Blvd, Saskatoon, SK S7N 3H5, Canada
| | - Helen Baulch
- Global Institute for Water Security, University of Saskatchewan, Innovation Blvd, Saskatoon, SK S7N 3H5, Canada; School of Environment and Sustainability, University of Saskatchewan, 117 Science Place, Saskatoon, SK S7N 5C8, Canada
| | - Jonathan K Challis
- Toxicology Centre, University of Saskatchewan, 44 Campus Dr, Saskatoon, SK S7N 5B3, Canada
| | - Yuwei Xie
- Toxicology Centre, University of Saskatchewan, 44 Campus Dr, Saskatoon, SK S7N 5B3, Canada
| | - John P Giesy
- Toxicology Centre, University of Saskatchewan, 44 Campus Dr, Saskatoon, SK S7N 5B3, Canada; Department of Veterinary Biomedical Sciences, University of Saskatchewan, 52 Campus Dr, Saskatoon, SK S7N 5B4, Canada; Department of Environmental Sciences, Baylor University, Waco, TX, 76706, USA; Department of Zoology and Center for Integrative Toxicology, Michigan State University, 426 Auditorium Road East Lansing, MI, 48824, USA
| | - Markus Hecker
- Toxicology Centre, University of Saskatchewan, 44 Campus Dr, Saskatoon, SK S7N 5B3, Canada; School of Environment and Sustainability, University of Saskatchewan, 117 Science Place, Saskatoon, SK S7N 5C8, Canada
| | - Markus Brinkmann
- Toxicology Centre, University of Saskatchewan, 44 Campus Dr, Saskatoon, SK S7N 5B3, Canada; Global Institute for Water Security, University of Saskatchewan, Innovation Blvd, Saskatoon, SK S7N 3H5, Canada; School of Environment and Sustainability, University of Saskatchewan, 117 Science Place, Saskatoon, SK S7N 5C8, Canada.
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3
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Tarek MH, Garner E. A proposed framework for the identification of indicator genes for monitoring antibiotic resistance in wastewater: Insights from metagenomic sequencing. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 854:158698. [PMID: 36108825 DOI: 10.1016/j.scitotenv.2022.158698] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 09/07/2022] [Accepted: 09/07/2022] [Indexed: 06/15/2023]
Abstract
Antibiotic resistance is one of the greatest threats to global human and animal health of our time. Municipal wastewater has been identified as a hotspot of antibiotic resistance contamination to water bodies. However, there are numerous potential antibiotic resistant pathogens and their associated antibiotic resistance genes (ARGs), making it difficult to implement routine monitoring that addresses the breadth of the problem. The objective of this study was to identify candidate indicator ARGs for monitoring antibiotic resistance in wastewater and receiving water bodies. We developed a framework to identify indicator ARGs that incorporated clinical relevance, abundance in wastewater, geographic ubiquity, environmental relevance, ARG mobility, associations with mobile genetic elements, and the availability of quantitative analytical methods. To identify indicator ARGs, published metagenomic sequencing data from 191 wastewater samples originating from 64 countries across the world were obtained from online public repositories. Through ARG annotation and network analysis, this framework revealed 56 candidate indicator ARGs distributed across four modules of strongly correlated ARGs, with one ARG from each module (oqxA, ermB, sul1, and mexE) proposed as a minimally redundant monitoring target. The results of this study provide the basis for antibiotic resistance surveillance and monitoring framework in wastewater and contaminated waterways.
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Affiliation(s)
- Mehedi Hasan Tarek
- Wadsworth Department of Civil & Environmental Engineering, West Virginia University, Morgantown, WV 26506, United States of America
| | - Emily Garner
- Wadsworth Department of Civil & Environmental Engineering, West Virginia University, Morgantown, WV 26506, United States of America.
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4
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Nava AR, Daneshian L, Sarma H. Antibiotic resistant genes in the environment-exploring surveillance methods and sustainable remediation strategies of antibiotics and ARGs. ENVIRONMENTAL RESEARCH 2022; 215:114212. [PMID: 36037921 DOI: 10.1016/j.envres.2022.114212] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 08/05/2022] [Accepted: 08/22/2022] [Indexed: 06/15/2023]
Abstract
Antibiotic Resistant Genes (ARGs) are an emerging environmental health threat due to the potential change in the human microbiome and selection for the emergence of antibiotic resistant bacteria. The rise of antibiotic resistant bacteria has caused a global health burden. The WHO (world health organization) predicts a rise in deaths due to antibiotic resistant infections. Since bacteria can acquire ARGs through horizontal transmission, it is important to assess the dissemination of antibioticresistant genes from anthropogenic sources. There are several sources of antibiotics, antibiotic resistant bacteria and genes in the environment. These include wastewater treatment plants, landfill leachate, agricultural, animal industrial sources and estuaries. The use of antibiotics is a worldwide practice that has resulted in the evolution of resistance to antibiotics. Our review provides a more comprehensive look into multiple sources of ARG's and antibiotics rather than one. Moreover, we focus on effective surveillance methods of ARGs and antibiotics and sustainable abiotic and biotic remediation strategies for removal and reduction of antibiotics and ARGs from both terrestrial and aquatic environments. Further, we consider the impact on public health as this problem cannot be addressed without a global transdisciplinary effort.
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Affiliation(s)
- Amy R Nava
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, 94305, USA.
| | - Leily Daneshian
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, 94305, USA.
| | - Hemen Sarma
- Bioremediation Technology Research Group, Department of Botany, Bodoland University, Rangalikhata, Deborgaon, Kokrajhar (BTR), Assam, 783370, India.
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5
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Ortúzar M, Esterhuizen M, Olicón-Hernández DR, González-López J, Aranda E. Pharmaceutical Pollution in Aquatic Environments: A Concise Review of Environmental Impacts and Bioremediation Systems. Front Microbiol 2022; 13:869332. [PMID: 35558129 PMCID: PMC9087044 DOI: 10.3389/fmicb.2022.869332] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 03/30/2022] [Indexed: 11/13/2022] Open
Abstract
The presence of emerging contaminants in the environment, such as pharmaceuticals, is a growing global concern. The excessive use of medication globally, together with the recalcitrance of pharmaceuticals in traditional wastewater treatment systems, has caused these compounds to present a severe environmental problem. In recent years, the increase in their availability, access and use of drugs has caused concentrations in water bodies to rise substantially. Considered as emerging contaminants, pharmaceuticals represent a challenge in the field of environmental remediation; therefore, alternative add-on systems for traditional wastewater treatment plants are continuously being developed to mitigate their impact and reduce their effects on the environment and human health. In this review, we describe the current status and impact of pharmaceutical compounds as emerging contaminants, focusing on their presence in water bodies, and analyzing the development of bioremediation systems, especially mycoremediation, for the removal of these pharmaceutical compounds with a special focus on fungal technologies.
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Affiliation(s)
- Maite Ortúzar
- Department of Microbiology and Genetics, Edificio Departamental, University of Salamanca, Salamanca, Spain
| | - Maranda Esterhuizen
- Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences, Finland and Helsinki Institute of Sustainability Science, University of Helsinki, Helsinki, Finland.,Joint Laboratory of Applied Ecotoxicology, Korea Institute of Science and Technology Europe, Saarbrücken, Germany.,University of Manitoba, Clayton H. Riddell Faculty of Environment, Earth, and Resources, Winnipeg, MB, Canada
| | - Darío Rafael Olicón-Hernández
- Instituto Politécnico Nacional, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Mexico City, Mexico
| | - Jesús González-López
- Environmental Microbiology Group, Institute of Water Research, University of Granada, Granada, Spain.,Department of Microbiology, Faculty of Pharmacy, University of Granada, Granada, Spain
| | - Elisabet Aranda
- Environmental Microbiology Group, Institute of Water Research, University of Granada, Granada, Spain.,Department of Microbiology, Faculty of Pharmacy, University of Granada, Granada, Spain
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6
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McCubbin KD, Anholt RM, de Jong E, Ida JA, Nóbrega DB, Kastelic JP, Conly JM, Götte M, McAllister TA, Orsel K, Lewis I, Jackson L, Plastow G, Wieden HJ, McCoy K, Leslie M, Robinson JL, Hardcastle L, Hollis A, Ashbolt NJ, Checkley S, Tyrrell GJ, Buret AG, Rennert-May E, Goddard E, Otto SJG, Barkema HW. Knowledge Gaps in the Understanding of Antimicrobial Resistance in Canada. Front Public Health 2021; 9:726484. [PMID: 34778169 PMCID: PMC8582488 DOI: 10.3389/fpubh.2021.726484] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 09/16/2021] [Indexed: 01/21/2023] Open
Abstract
Current limitations in the understanding and control of antimicrobial resistance (AMR) in Canada are described through a comprehensive review focusing on: (1) treatment optimization; (2) surveillance of antimicrobial use and AMR; and (3) prevention of transmission of AMR. Without addressing gaps in identified areas, sustained progress in AMR mitigation is unlikely. Expert opinions and perspectives contributed to prioritizing identified gaps. Using Canada as an example, this review emphasizes the importance and necessity of a One Health approach for understanding and mitigating AMR. Specifically, antimicrobial use in human, animal, crop, and environmental sectors cannot be regarded as independent; therefore, a One Health approach is needed in AMR research and understanding, current surveillance efforts, and policy. Discussions regarding addressing described knowledge gaps are separated into four categories: (1) further research; (2) increased capacity/resources; (3) increased prescriber/end-user knowledge; and (4) policy development/enforcement. This review highlights the research and increased capacity and resources to generate new knowledge and implement recommendations needed to address all identified gaps, including economic, social, and environmental considerations. More prescriber/end-user knowledge and policy development/enforcement are needed, but must be informed by realistic recommendations, with input from all relevant stakeholders. For most knowledge gaps, important next steps are uncertain. In conclusion, identified knowledge gaps underlined the need for AMR policy decisions to be considered in a One Health framework, while highlighting critical needs to achieve realistic and meaningful progress.
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Affiliation(s)
- Kayley D. McCubbin
- Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
| | | | - Ellen de Jong
- Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
| | - Jennifer A. Ida
- Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
| | - Diego B. Nóbrega
- Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
| | - John P. Kastelic
- Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
| | - John M. Conly
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
- O'Brien Institute of Public Health, University of Calgary, Calgary, AB, Canada
- Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada
- Department of Microbiology, Immunology and Infectious Diseases, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- Department of Pathology and Laboratory Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- Alberta Health Services, Calgary, AB, Canada
| | - Matthias Götte
- Department of Medical Microbiology and Immunology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Tim A. McAllister
- Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, AB, Canada
| | - Karin Orsel
- Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
| | - Ian Lewis
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, AB, Canada
| | - Leland Jackson
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, AB, Canada
| | - Graham Plastow
- Department of Agricultural, Food and Nutritional Science, Faculty of Agricultural, Life and Environmental Sciences, University of Alberta, Edmonton, AB, Canada
| | - Hans-Joachim Wieden
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, AB, Canada
| | - Kathy McCoy
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
- Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Myles Leslie
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
- O'Brien Institute of Public Health, University of Calgary, Calgary, AB, Canada
- Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- School of Public Policy, University of Calgary, Calgary, AB, Canada
| | - Joan L. Robinson
- Department of Pediatrics, Faculty of Medicine, University of Alberta, Edmonton, AB, Canada
| | - Lorian Hardcastle
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
- O'Brien Institute of Public Health, University of Calgary, Calgary, AB, Canada
- Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- Faculty of Law, University of Calgary, Calgary, AB, Canada
| | - Aidan Hollis
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
- O'Brien Institute of Public Health, University of Calgary, Calgary, AB, Canada
- Department of Economics, Faculty of Arts, University of Calgary, Calgary, AB, Canada
| | - Nicholas J. Ashbolt
- Faculty of Science and Engineering, Southern Cross University, Lismore, NSW, Australia
| | - Sylvia Checkley
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
- O'Brien Institute of Public Health, University of Calgary, Calgary, AB, Canada
- Department of Microbiology, Immunology and Infectious Diseases, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
| | - Gregory J. Tyrrell
- Alberta Precision Laboratories, Alberta Health Services, Calgary, AB, Canada
- Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, University of Alberta, Calgary, AB, Canada
| | - André G. Buret
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
- Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, AB, Canada
| | - Elissa Rennert-May
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
- O'Brien Institute of Public Health, University of Calgary, Calgary, AB, Canada
- Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada
- Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- Alberta Health Services, Calgary, AB, Canada
- Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Ellen Goddard
- Department of Resource Economics and Environmental Sociology, Faculty of Agriculture, Life and Environmental Science, University of Alberta, Edmonton, AB, Canada
| | - Simon J. G. Otto
- HEAT-AMR Research Group, School of Public Health, University of Alberta, Edmonton, AB, Canada
- Thematic Area Lead, Healthy Environments, Centre for Healthy Communities, School of Public Health, University of Alberta, Edmonton, AB, Canada
| | - Herman W. Barkema
- Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
- One Health at UCalgary, University of Calgary, Calgary, AB, Canada
- O'Brien Institute of Public Health, University of Calgary, Calgary, AB, Canada
- Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada
- Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
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7
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Lai FY, Muziasari W, Virta M, Wiberg K, Ahrens L. Profiles of environmental antibiotic resistomes in the urban aquatic recipients of Sweden using high-throughput quantitative PCR analysis. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 287:117651. [PMID: 34426396 DOI: 10.1016/j.envpol.2021.117651] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 06/13/2021] [Accepted: 06/21/2021] [Indexed: 06/13/2023]
Abstract
Antibiotic resistance in aquatic ecosystems presents an environmental health issue worldwide. Urban recipient water quality is susceptible to effluent discharges with antibiotic resistance contaminants and needs to be protected, particularly for those as sources of drinking water production. Knowledge on aquatic resistome profiles in downstream of wastewater treatment plants allows a better understanding of the extent to which antibiotic resistance contaminants emerge and spread in recipient waters, but such information remains very limited in Sweden. The key objective of this study was to determine the resistome profiles of numerous antibiotic resistance genes (ARGs), mobile genetic elements (MGEs) and other genes in urban recipient water systems connected to Sweden's major drinking water reservoir. This was achieved through analysis of surface water samples for 296 genes using high-throughput quantitative PCR arrays. A total of 167 genes were detected in at least one of the samples, including 150 ARGs conferring resistance to 11 classes of antibiotics, 7 integrase MGEs and 9 other genes. There was a spatial difference in the resistome profiles with the greatest average relative abundance of resistance genes observed in the water body of Västerås followed by Uppsala, Stockholm and Eskilstuna, as similar to the general pattern of the antibiotic sales for these regions. ARGs against β-lactams and sulfonamides showed the highest average relative abundance in the studied water bodies, while vancomycin resistance genes were only found in the Uppsala water environment. Generally, the recipient water bodies were detected with higher numbers of genes and greater relative abundances as compared to the upstream sites. Anthropogenic pollution, i.e., wastewater discharge, in the recipient water was also reflected by the finding of intI, sul1 and crAssphage. Overall, this study provided the first quantitative assessment of aquatic environmental resistomes in Sweden, highlighting the widespread of antibiotic resistance contaminants in urban recipient waters.
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Affiliation(s)
- Foon Yin Lai
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU), Box 7050, SE-750 07, Uppsala, Sweden.
| | - Windi Muziasari
- Department of Food and Environmental Sciences, Division of Microbiology and Biotechnology, University of Helsinki, Viikinkaari 9, Helsinki, 00014, Finland; Resistomap Oy, Helsinki, Finland
| | - Marko Virta
- Department of Food and Environmental Sciences, Division of Microbiology and Biotechnology, University of Helsinki, Viikinkaari 9, Helsinki, 00014, Finland
| | - Karin Wiberg
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU), Box 7050, SE-750 07, Uppsala, Sweden
| | - Lutz Ahrens
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU), Box 7050, SE-750 07, Uppsala, Sweden
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8
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Makowska N, Bresa K, Koczura R, Philips A, Nowis K, Mokracka J. Urban wastewater as a conduit for pathogenic Gram-positive bacteria and genes encoding resistance to β-lactams and glycopeptides. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 765:144176. [PMID: 33385807 DOI: 10.1016/j.scitotenv.2020.144176] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 11/19/2020] [Accepted: 11/23/2020] [Indexed: 06/12/2023]
Abstract
The emergence and spread of clinical pathogens, antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the environment pose a direct threat to human and animal health worldwide. In this study, we analyzed qualitatively and quantitatively urban sewage resistome for the occurrence of genes encoding resistance to β-lactams and glycopeptides in the genomes of culturable bacteria, as well as in the wastewater metagenome of the Central Wastewater Treatment Plant in Koziegłowy (Poland). Moreover, we estimated the presence of pathogenic Gram-positive bacteria in wastewater based on analysis of species-specific virulence genes in the wastewater metagenome. The results show that the final effluent contains alarm pathogens with particularly dangerous mechanisms of antibiotic resistance, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). We also noticed that during the wastewater treatment, there is an increase in the frequency of MRSA and VRE. Furthermore, the results prove the effective removal of vanA, but at the same time show that wastewater treatment increases the relative abundance of mecA and virulence genes (groES and sec), indicating the presence of clinical pathogens E. faecalis and S. aureus in the effluent released to surface waters. We also observed an increase in the relative abundance of mecA and vanA genes already in the aeration tank, which suggests accumulation of contaminants affecting enhanced selection and HGT processes in the activated sludge. Moreover, we found a relation between the taxonomic composition and the copy number of ARGs as well as the presence of pathogens at various stages of wastewater treatment. The presence of clinically relevant pathogens, ARB, including multi-resistant bacteria, and ARGs in the effluent indicates that wastewater treatment plant play a key role in the existence of pathogens and antimicrobial resistance spreading pathway in the environment and human communities, which is a direct threat to public health and environmental protection.
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Affiliation(s)
- Nicoletta Makowska
- Department of Microbiology, Faculty of Biology, Adam Mickiewicz University in Poznań, Poznań, Poland; Department of Molecular Genetics, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland
| | - Katarzyna Bresa
- Department of Microbiology, Faculty of Biology, Adam Mickiewicz University in Poznań, Poznań, Poland
| | - Ryszard Koczura
- Department of Microbiology, Faculty of Biology, Adam Mickiewicz University in Poznań, Poznań, Poland
| | - Anna Philips
- European Center for Bioinformatics and Genomics, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland
| | - Katarzyna Nowis
- European Center for Bioinformatics and Genomics, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland
| | - Joanna Mokracka
- Department of Microbiology, Faculty of Biology, Adam Mickiewicz University in Poznań, Poznań, Poland.
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Cooper AL, Carter C, McLeod H, Wright M, Sritharan P, Tamber S, Wong A, Carrillo CD, Blais BW. Detection of carbapenem-resistance genes in bacteria isolated from wastewater in Ontario. Facets (Ott) 2021. [DOI: 10.1139/facets-2020-0101] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Bacterial carbapenem resistance is a major public health concern since these antimicrobials are often the last resort to treat serious human infections. To evaluate methodologies for detection of carbapenem resistance, carbapenem-tolerant bacteria were isolated from wastewater treatment plants in Toronto, Ottawa, and Arnprior, Ontario. A total of 135 carbapenem-tolerant bacteria were recovered. Polymerase chain reaction (PCR) indicated the presence of carbapenem hydrolysing enzymes KPC ( n = 10), GES ( n = 5), VIM ( n = 7), and IMP ( n = 1), and β-lactamases TEM ( n = 7), PER ( n = 1), and OXA-variants ( n = 16). A subset of 46 isolates were sequenced and analysed using ResFinder and CARD-RGI. Both programs detected carbapenem resistance genes in 35 sequenced isolates and antimicrobial resistance genes (ARGs) conferring resistance to multiple class of other antibiotics. Where β-lactamase resistance genes were not initially identified, lowering the thresholds for ARG detection enabled identification of closely related β-lactamases. However, no known carbapenem resistance genes were found in seven sequenced Pseudomonas spp. isolates. Also of note was a multi-drug-resistant Klebsiella pneumoniae isolate from Ottawa, which harboured resistance to seven antimicrobial classes including β-lactams. These results highlight the diversity of genes encoding carbapenem resistance in Ontario and the utility of whole genome sequencing over PCR for ARG detection where resistance may result from an assortment of genes.
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Affiliation(s)
- Ashley L. Cooper
- Research and Development, Canadian Food Inspection Agency, Ottawa, ON K1A 0Y9, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Cassandra Carter
- Applied Science and Environmental Technology, Algonquin College, Ottawa, ON K2G 1V8, Canada
| | - Hana McLeod
- Applied Science and Environmental Technology, Algonquin College, Ottawa, ON K2G 1V8, Canada
| | - Marie Wright
- Applied Science and Environmental Technology, Algonquin College, Ottawa, ON K2G 1V8, Canada
| | - Prithika Sritharan
- Applied Science and Environmental Technology, Algonquin College, Ottawa, ON K2G 1V8, Canada
| | - Sandeep Tamber
- Microbiology Research Division, Bureau of Microbial Hazards, Health Canada, Ottawa, ON K1A 0K9, Canada
| | - Alex Wong
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Catherine D. Carrillo
- Research and Development, Canadian Food Inspection Agency, Ottawa, ON K1A 0Y9, Canada
| | - Burton W. Blais
- Research and Development, Canadian Food Inspection Agency, Ottawa, ON K1A 0Y9, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
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10
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Role of wastewater treatment plants on environmental abundance of Antimicrobial Resistance Genes in Chilean rivers. Int J Hyg Environ Health 2019; 223:56-64. [PMID: 31722832 DOI: 10.1016/j.ijheh.2019.10.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 10/04/2019] [Accepted: 10/12/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND Point sources such as wastewater treatment plants (WWTPs) commonly discharge their effluent into rivers. Their waste may include antibiotic residues, disinfectants, antibiotic resistant bacteria (ARB), and Antimicrobial Resistance Genes (ARG). There is evidence that ARG can be found in the natural environment, but attribution to specific point sources is lacking. OBJECTIVES The goal of this study was to assess the release and dissemination of ARG from three WWTPs in southern Chile via two pathways: through the river systems, and through wild birds. METHODS A longitudinal study was conducted, collecting river sediment samples at different distances both upstream and downstream from each WWTP. Wild birds were sampled from around one of the WWTPs once a month for 13 months. A microfluidic q-PCR approach was used to quantify 48 genes covering different molecular mechanisms of resistance, and data was analyzed using ordination methods and linear mixed regression models. RESULTS There was a statistically significant increase downstream from the WWTPs (p < 0.05) for 17 ARG, but the downstream dissemination through the rivers was not clear. Beta-lactamase genes blaKPC, blaTEM, and blaSHV were the most abundant in birds, with higher abundance of blaSHV in migratory species compared to resident species (p < 0.05). The gene profile was more similar between the migratory and resident bird groups compared to the WWTP gene profile. CONCLUSIONS While results from this study indicate an influence of WWTPs on ARG abundance in the rivers, the biological significance of this increase and the extent of the WWTPs influence are unclear. In addition, wild birds were found to play a role in disseminating ARG, although association to the specific WWTP could not be ascertained.
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11
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Cacace D, Fatta-Kassinos D, Manaia CM, Cytryn E, Kreuzinger N, Rizzo L, Karaolia P, Schwartz T, Alexander J, Merlin C, Garelick H, Schmitt H, de Vries D, Schwermer CU, Meric S, Ozkal CB, Pons MN, Kneis D, Berendonk TU. Antibiotic resistance genes in treated wastewater and in the receiving water bodies: A pan-European survey of urban settings. WATER RESEARCH 2019; 162:320-330. [PMID: 31288142 DOI: 10.1016/j.watres.2019.06.039] [Citation(s) in RCA: 177] [Impact Index Per Article: 35.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 06/14/2019] [Accepted: 06/15/2019] [Indexed: 05/05/2023]
Abstract
There is increasing public concern regarding the fate of antibiotic resistance genes (ARGs) during wastewater treatment, their persistence during the treatment process and their potential impacts on the receiving water bodies. In this study, we used quantitative PCR (qPCR) to determine the abundance of nine ARGs and a class 1 integron associated integrase gene in 16 wastewater treatment plant (WWTP) effluents from ten different European countries. In order to assess the impact on the receiving water bodies, gene abundances in the latter were also analysed. Six out of the nine ARGs analysed were detected in all effluent and river water samples. Among the quantified genes, intI1 and sul1 were the most abundant. Our results demonstrate that European WWTP contribute to the enrichment of the resistome in the receiving water bodies with the particular impact being dependent on the effluent load and local hydrological conditions. The ARGs concentrations in WWTP effluents were found to be inversely correlated to the number of implemented biological treatment steps, indicating a possible option for WWTP management. Furthermore, this study has identified blaOXA-58 as a possible resistance gene for future studies investigating the impact of WWTPs on their receiving water.
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Affiliation(s)
- Damiano Cacace
- Environmental Sciences Technische Universität Dresden, Institute of Hydrobiology, 01062, Dresden, Zellescher Weg 40, Germany
| | - Despo Fatta-Kassinos
- Department of Civil and Environmental Engineering and Nireas-International Water Research Center, School of Engineering, University of Cyprus, P.O. Box 20537, 1678, Nicosia, Cyprus
| | - Celia M Manaia
- Universidade Católica Portuguesa, CBQF - Centro de Biotecnologia e Química Fina - Laboratório Associado, Escola Superior de Biotecnologia, Portugal
| | - Eddie Cytryn
- The Institute of Soil, Water and Environmental Sciences, The Volcani Center, Agricultural Research Organization, Bet-Dagan, Israel
| | - Norbert Kreuzinger
- Institute for Water Quality and Resource Management, Vienna University of Technology, Karlsplatz 13, 1040, Vienna, Austria
| | - Luigi Rizzo
- Department of Civil Engineering, University of Salerno, Via Ponte Don Melillo 1, 84084, Fisciano (SA), Italy
| | - Popi Karaolia
- Department of Civil and Environmental Engineering and Nireas-International Water Research Center, School of Engineering, University of Cyprus, P.O. Box 20537, 1678, Nicosia, Cyprus
| | - Thomas Schwartz
- Karlsruhe Institute of Technology (KIT) - Campus North, Institute of Functional Interfaces (IFG), P.O. Box 3640, 76021, Karlsruhe, Germany
| | - Johannes Alexander
- Karlsruhe Institute of Technology (KIT) - Campus North, Institute of Functional Interfaces (IFG), P.O. Box 3640, 76021, Karlsruhe, Germany
| | - Christophe Merlin
- Laboratoire de Chimie Physique et Microbiologie pour Les Matériaux et L'Environnement (LCPME), UMR 7564, CNRS-Université de Lorraine, Vandoeuvre-lès-Nancy F, 54500, France
| | - Hemda Garelick
- Department of Natural Science, Faculty of Science and Technology, Middlesex University, The Burroughs, London, NW4 4BT, UK
| | - Heike Schmitt
- Institute for Risk Assessment Sciences, Utrecht University, Yalelaan 2, 3584, CM Utrecht, the Netherlands
| | - Daisy de Vries
- Institute for Risk Assessment Sciences, Utrecht University, Yalelaan 2, 3584, CM Utrecht, the Netherlands
| | - Carsten U Schwermer
- Norwegian Institute for Water Research (NIVA), Gaustadalléen 21, 0349, Oslo, Norway
| | - Sureyya Meric
- Corlu Engineering Faculty, Environmental Engineering Department, Namık Kemal Üniversitesi, Çorlu, 59860, Tekirdağ, Turkey
| | - Can Burak Ozkal
- Corlu Engineering Faculty, Environmental Engineering Department, Namık Kemal Üniversitesi, Çorlu, 59860, Tekirdağ, Turkey
| | - Marie-Noelle Pons
- Laboratoire Réactions et Génie des Procédés, CNRS-Université de Lorraine, 1, Rue Grandville, BP 20451, 54001, Nancy Cedex, France
| | - David Kneis
- Environmental Sciences Technische Universität Dresden, Institute of Hydrobiology, 01062, Dresden, Zellescher Weg 40, Germany
| | - Thomas U Berendonk
- Environmental Sciences Technische Universität Dresden, Institute of Hydrobiology, 01062, Dresden, Zellescher Weg 40, Germany.
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12
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Hayward JL, Huang Y, Yost CK, Hansen LT, Lake C, Tong A, Jamieson RC. Lateral flow sand filters are effective for removal of antibiotic resistance genes from domestic wastewater. WATER RESEARCH 2019; 162:482-491. [PMID: 31306951 DOI: 10.1016/j.watres.2019.07.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 06/28/2019] [Accepted: 07/03/2019] [Indexed: 06/10/2023]
Abstract
The ability of lateral flow sand filters, used as on-site wastewater treatment systems (OWTS), to remove antibiotic resistance genes (ARGs), antibiotic resistant bacteria (ARB), and other relevant genetic markers (HF183, 16S rRNA, and int1) was assessed. Municipal wastewater was settled in a septic tank prior to loading into six pilot-scale lateral flow sand filters comprised of three different sand media types, at 5 and 30% slopes. The sand filters were sampled bi-weekly for: 9 ARGs and 3 other complimentary gene markers (sul1, sul2, qnrS, tetO, ermB, blaTEM, blaCTX-M, mecA, vanA, int1, HF183, 16S rRNA), and conventional microbial and water quality indicators, from July to November in 2017, and four times in the summer of 2018. The sand filters were observed to attenuate 7 of the ARGs to mostly below 2 log gene copies per mL. Log reductions ranging from 2.9 to 5.4 log were observed for the removal of absolute abundances of ARGs from septic tank effluent in 5 of the 6 sand filters. The fine-grained filter on the 5% slope did not perform as well for ARG attenuation due to hydraulic failure. The apportionment of cell-associated versus cell-free DNA was determined for the gene markers and this indicated that the genes were primarily carried intracellularly. Average log reductions of ARB with resistance to either sulfamethoxazole, erythromycin, or tetracycline were approximately 2.3 log CFU per mL within the filters compared to the septic tank effluent. This field study provides in-depth insights into the attenuation of ARB, ARGs, and their genetic compartmentalization in variably saturated sand OWTS. Overall, this type of OWTS was found to pose little risk of antimicrobial resistance contamination spread into surrounding environments when proper hydraulic function was maintained.
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Affiliation(s)
- Jennifer L Hayward
- Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, 1360 Barrington Street, Halifax, Nova Scotia, B3H 4R2, Canada.
| | - Yannan Huang
- Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, 1360 Barrington Street, Halifax, Nova Scotia, B3H 4R2, Canada.
| | - Christopher K Yost
- Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, Saskatchewan, S4S 0A2, Canada.
| | | | - Craig Lake
- Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, 1360 Barrington Street, Halifax, Nova Scotia, B3H 4R2, Canada.
| | - Anthony Tong
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, Nova Scotia, B4P 2R6, Canada.
| | - Rob C Jamieson
- Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, 1360 Barrington Street, Halifax, Nova Scotia, B3H 4R2, Canada.
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McConnell MM, Hansen LT, Neudorf KD, Hayward JL, Jamieson RC, Yost CK, Tong A. Sources of Antibiotic Resistance Genes in a Rural River System. JOURNAL OF ENVIRONMENTAL QUALITY 2018; 47:997-1005. [PMID: 30272774 DOI: 10.2134/jeq2017.12.0477] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The increasing prevalence of antibiotic resistance genes (ARGs) in the environment is problematic due to the risk of horizontal gene transfer and development of antibiotic resistant pathogenic bacteria. Using a suite of monitoring tools, this study aimed to investigate the sources of ARGs in a rural river system in Nova Scotia, Canada. The monitoring program specifically focused on the relative contribution of ARGs from a single tertiary-level wastewater treatment plant (WWTP) in comparison to contributions from the upgradient rural, sparsely developed, watershed. The overall gene concentration significantly ( < 0.05) increased downstream from the WWTP, suggesting that tertiary-level treatment still contributes ARGs to the environment. As a general trend, ARG concentrations upstream were found to decrease as proximity to human-impacted areas decreased; however, many ARGs remained above detection limits in headwater river samples, which suggested their ubiquitous presence in this watershed in the absence of obvious pollution sources. Significant correlations with ARGs were found for human fecal marker, and some antibiotics, suggesting that these markers may be useful for prediction and understanding of ARG levels and sources in rural rivers.
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