Transformation products of antibiotics exert antimicrobial resistance with comparable selective pressure to parent compounds

Antibiotic transformation products (TPs) are commonly found in wastewater and aquatic environments, yet their role in driving antimicrobial resistance (AMR) is poorly understood. Unlike their parent compounds, TPs are often excluded from environmental risk assessments despite their persistence and potential bioactivity. In this study, environmentally relevant concentrations and wastewater-derived microbial communities were used to assess the selective pressure of TPs. A growth-based SELECT assay revealed that several TPs had similar resistance-selective effects than their parent antibiotics. In a 7-day evolution experiment, qPCR results showed that TPs such as desmethyl ofloxacin and N-acetyl sulfamethoxazole induced significant enrichment of the intI1 gene. These trends were consistent across fluoroquinolone, sulfonamide, and MLS antibiotic classes. Our findings highlight the overlooked role of TPs in AMR selection and support their inclusion in surveillance and environmental risk assessments.

Please note, Pooja Lakhey is a PhD student and this is a student progress review.