Environmental Occurrence and Antimicrobial Resistance Potential of Carbapenems – Last-Resort Antibiotics

The misuse of antibiotics in human and veterinary practices is a major driver of antimicrobial resistance (AMR), associated with an estimated 1.3 million deaths globally in 2019. Antibiotics have been detected in aquatic environments, yet monitoring of the last resort antibiotics – carbapenems – remains scarce. Their structural similarity to penicillins and excretion in humans indicates that carbapenems reach wastewater and surface waters, exerting selective pressure that fosters AMR. Nevertheless, prior to this study, o evidence exists to verify these claims.<br/>In this study, conducted under the Environmental Fate of Novel Antibiotics project, we developed and validated a sensitive LC-MS/MS method for quantifying six carbapenems (biapenem, doripenem, ertapenem, faropenem, imipenem, and meropenem) in environmental waters. The method was applied to Danish hospital wastewater and surface waters, where several carbapenems were detected at environmentally relevant concentrations.<br/>Recognizing that carbapenems are unstable and that antibiotic transformation products (TPs) may retain biological activity, we further investigated the fate of carbapenems. Transformation products of ertapenem, faropenem, imipenem and meropenem were observed under environmentally relevant conditions, and their potential role in AMR is under evaluation.<br/>By studying both parent compounds and transformation products, we provide new insights into the environmental persistence of carbapenems and their possible contribution to AMR. Our findings highlight the overlooked persistence and transformation of carbapenems, underscoring their potential role in driving AMR in aquatic environments.