Antibiotics and antibiotic resistance genes in aquatic environments in China:Occurrences and risks
Antibiotics are recognized as emerging contaminants worldwide.Specifically,China has included antibiotics in its list of emerging contaminants for priority management and control as part of the 14th Five-Year Plan.After being consumed in clinical settings and livestock farming,antibiotics are largely excreted into the environment.Among various environmental media,aquatic environments serve as significant reservoirs for antibiotics due to the influx of both point and non-point source wastewater containing antibiotics,including municipal,pharmaceutical,and livestock wastewater.Consequently,assessing and managing the risks associated with antibiotics in aquatic environments is of utmost importance.This study initially reviews the occurrence of antibiotics in aquatic environments.The findings reveal the pervasive presence of antibiotics in Chinese rivers,with macrolides,tetracyclines,sulfonamides,fluoroquinolones,and β-lactams ranking among the top five antibiotics in terms of abundance and detection frequency.The presence of antibiotics significantly contributes to the persistence,development,and transmission of antibiotic resistance genes(ARGs)in Chinese rivers.Despite the occurrence of antibiotics and ARGs in aquatic environments in China,the risks associated with antibiotics have not been adequately described.Typically,indicators such as Persistence,Bioaccumulation,and Toxicity,collectively known as the P-B-T framework,are commonly used to assess the risk of emerging contaminants,including antibiotics.However,this framework does not align well with antibiotics since they do not conform to the typical profile of Persistent Bioaccumulative Toxic Substances.Consequently,the Predicted No-Effect Concentration(PNEC)for antibiotics usually falls within the range of μg/L to mg/L,which is significantly higher than the typical levels of antibiotic abundance found in aquatic environments(ng/L to μg/L).Thus,there is an urgent need to propose a novel risk assessment method specifically tailored for antibiotics in aquatic environments.Recognizing the critical role of antibiotics in inducing bacterial resistance,we propose a multi-dimensional antibiotic resistance risk assessment framework(MARA)for antibiotics in aquatic environments.In details,at the genetic level,antibiotic selective pressure can lead to genetic mutations,which represents the predominant pathway for the generation of ARGs.At the cellular level,antibiotic selective pressure aids bacterial hosts in retaining plasmids carrying ARGs.At the population and community levels,antibiotic selective pressure promotes horizontal gene transfer,resulting in the acquisition of antibiotic resistance by initially sensitive strains.Furthermore,antibiotic selective pressure assists antibiotic-resistant bacteria in outcompeting antibiotic-sensitive bacteria at the community level,contributing to the development of bacterial resistance.Collectively,dose-response data for antibiotic-induced bacterial resistance at the genetic,cellular,population,and community levels will be acquired,and the PNEC will be established accordingly.Finally,we propose strategies to advance fundamental research innovation,thereby facilitating the practical application of MARA.These strategies encompass advancing dose-response studies on antibiotics that induce bacterial resistance and investigating the impact of antibiotic bioavailability,bacterial growth,and metabolism status on the dose-response relationship.Overall,this study endeavors to offer scientific and technological support for the treatment,management,and control of antibiotics in China.
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