Since the discovery of penicillin by Alexander Flemming and its clinical introduction in 1941, antibiotics have been used to successfully treat infectious diseases in millions of people and reduce patient mortality. The golden age of antibiotics occurred between the 1940s and ’90s, when the majority of the antibiotics we use today were discovered. However, the current reality is that bacterial antibiotic resistance has become an increasing threat to public health. The battle to mitigate this resistance is a global problem and is compounded by the fact pharmaceutical companies have curtailed investment into the development of new antibiotics.
Antibiotic misuse and overuse in the health-care sector and agricultural industry has led to the development of antibiotic-resistant bacteria in several sectors and environments. The severity of the threat has been observed in recent outbreaks of antibiotic resistance, such as the multidrug-resistant shigellosis outbreak in the United States and Puerto Rico between May 2014 and February 2015. There have been efforts to help control the misuse of antibiotics, such as the European Union’s policy to improve the regulation of clinical prescriptions and the use of antibiotics in animal husbandry. However, they often do not consider other potential reservoirs for antibiotic-resistant elements, such as agriculture, health-care settings, and wastewater treatment plants.
Breeding grounds for growth
Excreted gut bacteria, which include antibiotic-resistant bacteria, are transported to wastewater treatment plants through domestic sewer lines. The rich organic nutrients within a wastewater plant are ideal for microbial growth—ripe to provide conditions that facilitate transfer of resistance genes within microbial communities. Therefore, wastewater plants can facilitate the development of antibiotic resistance in pathogens.
Throughout Canada, there are thousands of wastewater plants that service different types of communities and employ various treatment processes. Recent improvements to treatment plants have focused on nitrogen and phosphorus removal, but the infrastructure is not specifically designed to remove emerging contaminants like antibiotic residues and antibiotic-resistant bacteria. Upgrades to facilities present the ideal timing to investigate the magnitude of antibiotic-resistant bacteria in different treatment plant effluents and explore options for mitigating release of antibiotic-resistant bacteria. It is essential we identify the role of the treatment process and how it could be promoting antibiotic resistance.
Understanding the risk
A multidisciplinary research team—including Rob Jamieson and Lisbeth Truelstrup Hansen from the University of Dalhousie; Anthony Tong from Acadia University; and Chris Yost from the University of Regina—was assembled to study this issue in wastewater treatment plants in Nova Scotia, Saskatchewan, Prince Edward Island, and Nunavut. The specific plants were selected in order to investigate different waste inputs and treatment processes. The project began in the summer of 2015 and involves collecting influent, effluent, and treatment water samples from the different plants. The abundance, diversity, and nature of the antibiotic resistance genes will be characterized to help identify mechanisms that control or drive the development of antibiotic-resistant bacterial communities in wastewater treatment facilities.
Both primary treatment systems and more complex tertiary plants that include biological nutrient processes will be studied, and the team will examine samples throughout multiple treatment processes. Sampling in Regina will occur before and after a treatment plant upgrade to allow for a comparison of different treatment options using the same influent source. The research will also monitor the presence of antibiotic-resistant bacteria and genes in water systems receiving effluent discharges to assess the risk of human exposure to antibiotic-resistant pathogens after wastewater has left the treatment facility. In Nunavut and Prince Edward Island, for example, the treatment plant effluent is discharged into coastal bays where fishing and clam harvesting occurs.
Overall, this study will help us understand where and how antibiotic-resistant genes could persist in wastewater treatment facilities and the risk they pose to human and environmental health. This study will also help identify wastewater treatment processes that mitigate the release of these materials into the environment and will contribute to advancing our abilities to protect water security in Canada.
Kara Neudorf is a postdoctoral fellow at Dalhousie University in Halifax.