pBI143 as a Process Indicator for Antibiotic Resistance Gene Removal through Activated Sludge Wastewater Treatment

Antibiotic-resistant genes (ARGs) persist through wastewater treatment, posing a critical threat to public health and environmental safety. Due to ARG diversity, monitoring during wastewater treatment remains challenging; a reliable process indicator could streamline ARG monitoring and reveal overall treatment performance. Here, we evaluated the removal of nine clinically and agriculturally relevant ARGs through an activated sludge wastewater treatment plant and evaluated plasmid pBI143, Carjivirus, and HF183 as process indicators for ARG removal. Wastewater samples from four treatment stages were collected over 15 nonconsecutive days. Mean log10 reduction values of the tested ARGs ranged from 2.29 (sul1) to 3.15 (blaTEM), and secondary treatment accounted for the highest reductions. pBI143 exhibited the highest concentration in influent (1.02 × 106 gc/mL) and final effluent (8.45 × 102 gc/mL), followed by Carjivirus and HF183. pBI143 strongly correlated (r ≥ 0.80) with six ARGs (tetW, tetQ, sul1, ermB, mefA, ampC) and moderately correlated (r ≥ 0.60) with three ARGs (blaTEM, blaOXA, vanA), outperforming HF183 and Carjivirus in overall association with ARGs. Given its high abundance and strong correlation with the tested ARGs, pBI143 shows promise as a process indicator for tracking ARG fate through wastewater treatment systems.