The discharge of untreated hospital effluents contributes to the dissemination of antimicrobials, resistance genes, and multidrug-resistant bacteria. Upon reaching aquatic ecosystems, these contaminants promote selective pressure and horizontal gene transfer of resistance determinants. In this scenario, sustainable technologies such as phytoremediation emerge as promising alternatives to mitigate antimicrobial resistance (AMR). This technique relies on the ability of certain plants to remove contaminants and microorganisms from water, acting as an ecotechnological barrier against AMR dissemination. The present study evaluated the potential of phytoremediation using Pistia stratiotes for the removal of antimicrobials, resistant bacteria, and associated resistance genes from hospital effluent.

Hospital effluent was collected in Lapa (Paraná, Brazil) and subjected to laboratory-scale treatment with P. stratiotes. Experiments were conducted in 1-L containers for seven days under controlled conditions. Two groups (n = 3) were tested: (1) effluent without plants and (2) effluent treated with P. stratiotes. After the experimental period, the effluent was analyzed for antimicrobials (tetracyclines and beta-lactams) using the TwinSensor test. Quantification of resistant bacteria was performed by serial dilution (10⁻⁵) and plating on ESBL medium. Resistant isolates were identified and quantified by colony-forming unit (CFU) counting, and carbapenemase genes (KPC, IMP, NDM, VIM, OXA-48) were detected using a combined rapid test (Medomics).

Resistance genes such as KPC, IMP, and NDM were detected, as well as the following antimicrobials: tetracycline (80 µg/L), oxytetracycline (60 µg/L), amoxicillin (2 µg/L), and penicillin (3 µg/L). Beta-lactam-resistant bacterial isolates included Klebsiella pneumoniae, Escherichia coli, Pseudomonas spp., and Proteus spp. Treatment with P. stratiotes led to complete removal of antimicrobials, total elimination of E. coli CFUs, and more than 99% reduction of the remaining resistant bacteria. The NDM gene was removed, while other genes persisted.

Pistia stratiotes demonstrated significant ability to remove antimicrobials, resistance genes, and resistant bacteria, representing a promising strategy for AMR mitigation within the One Health framework.