Retrospective analysis of the global antibiotic residues that exceed the predicted no effect concentration for antimicrobial resistance in various environmental matrices

Background Antimicrobial resistance (AMR) is a growing public health concern. Recent research has suggested that interactions between pathogens and antibiotic residues in various environmental matrices promote the development and spread of AMR in the environment. The levels of antibiotic residues in the aquatic environment have been analysed globally. Recently, Predicted No Effect Environmental Concentration (PNEC) values for many antibiotics have been suggested, based on their estimated minimal selective concentrations for selected bacterial species. The PNEC values can serve as a guide on the maximum levels of antibiotic residues in an environmental matrix, below which resistance is unlikely to develop. Aim We aimed to determine which of the antibiotics, considered as “priority antibiotics” by the World Health Organisation (WHO), most frequently exceeded their PNEC values in the global aquatic environment. Methods We obtained data from the German Environment Agency pharmaceutical database on means, medians or single values of 12 antibiotic types in five different environmental matrices [municipal wastewater treatment plant effluent, industrial wastewater effluent, hospital wastewater effluent, surface water, and drinking water] across 47 countries. We compared the mean levels of the 12 antibiotics in each environmental matrix to their suggested PNEC values to determine which antibiotic types exceeded PNEC and were most likely to select for resistance. We also determined which environmental matrices and countries had the highest burden of antibiotic residues. Results Our study revealed that 7.9% of all analyses of antibiotic residues performed in the environmental matrices globally exceeded PNEC. Ciprofloxacin and clarithromycin had the greatest proportion (>30%) of residues exceeding PNEC. Hospital wastewater and industrial wastewater had the highest burden of antibiotic residues exceeding PNEC. No antibiotics exceeded PNEC in drinking water. Conclusion While most environmental monitoring studies have focused on municipal wastewater treatment plants, the limited number of studies on hospital wastewater and industrial wastewater revealed that a large number of antibiotic residues coming from these sources exceeded their PNEC values. Our study highlights the importance of implementing on-site treatment systems that aim to destroy antibiotics prior to discharging wastewater to surface waters. Attention needs to be focused on the role that environmental matrices, particularly our wastewater sites, play in promoting antibiotic resistance. Novel treatment technologies need to be developed and implemented to increase the removal efficiencies of treatment plants and from antibiotic manufacturing, and decrease the discharge of antibiotic residues into aquatic environments.