Abstract
Antimicrobial resistance (AMR) in the environment is a globally concerning issue. This study sought to improve the understanding of human health risks from an environmental AMR proliferation perspective. Surface water concentrations of 11 most used antibiotics in the United States were simulated for the Columbia and Sacramento River watersheds using the Pharmaceutical Assessment and Transport Evaluation (PhATE) model. The predicted environmental concentrations (PECs) and literature-reported measured environmental concentrations (MECs) of antibiotics were compared to the predicted no effect concentrations (PNECs) of three frameworks proposed as protective of AMR selection. For all of the studied antibiotics, PECs (except for moxifloxacin, a 4th generation fluoroquinolone), and at least one published MEC, were above the safe limit proposed by at least one of the three frameworks. The results indicate that a variety of different antibiotics with different mechanisms of action and physico-chemical properties are likely in environmental compartments at or above the concentrations currently proposed as safe from an AMR proliferation perspective. Understanding environmental occurrence of antibiotics is important for assessing environmental exposures and, when compared to PNECs for resistance selection, can—either alone or in combination with other methods— more specifically indicate where there are potential risks of AMR proliferation.
Highlights
Subtherapeutic levels of antibiotics in the aquatic environment pose a potential threat to both human health and the integrity of natural ecosystems
The Pharmaceutical Assessment and Transport Evaluation (PhATE) model was applied to the Sacramento and Columbia River watersheds, assuming two different river flows and four different loss scenarios: 1) “All”, which included in stream loss and wastewater treatment plant (WWTP) loss; 2) “In Stream”, which included in stream loss only; 3) “WWTP”, which included loss from WWTPs only; and 4) “None”, which was the most conservative assumption with neither WWTP or in stream loss
We simulated predicted environmental concentrations (PECs) of 11 most used antibiotics, which belong to nine different sub-classes, for two North-American river watersheds and compared the resulting PECs to predicted no effect concentrations (PNECs) of three frameworks which address the issue of antimicrobial resistance (AMR) propagation
Summary
Subtherapeutic levels of antibiotics in the aquatic environment pose a potential threat to both human health and the integrity of natural ecosystems. Despite the antibiotic-specific assessment re quirements, these may not be followed in cases where the released amounts of antibiotics are predicted to be low These regulations overlook the aspect that antibiotic effects can have broader impacts than causing toxicity. The emergence and mobi lization of novel resistance genes in environmental bacteria and sub sequent transfer to human pathogens has been identified as a major human health risk associated with environmental AMR (BengtssonPalme et al, 2018). These events are more likely to occur in environ ments under strong selection pressures such as these exerted by
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