Occurrence and seasonal variation of antibiotic resistance genes in wastewater and their dissemination to the Ganges River, Northern India

Antibiotic resistance has emerged as one of the most significant public health concerns of the twenty-first century. The excessive and inappropriate use of antibiotics has accelerated the proliferation of antibiotic-resistant bacteria (ARB) and genes (ARGs). Rapid urbanization and anthropogenic activities further facilitate the dissemination of ARB and ARGs into downstream river ecosystems through the discharge of treated effluents from wastewater treatment plants (WWTPs). The study investigates the occurrence, seasonal variations, and distribution of selected ARGs (blaNDM-1, blaSHV, blaCTX-M, ermB, qnrS, and vanA) and intI1 gene in WWTPs and downstream river environments. Samples (inlet, treated wastewater, and activated sludge) were collected during the winter and summer seasons over 1 year from three WWTPs employing different treatment technologies, as well as from the Ganges River (water and sediment) in North Indian cities: Kanpur, Prayagraj, and Varanasi. The results indicated that WWTPs significantly reduced ARB and ARG levels in treated effluents, a marked increase in their abundance was observed in the downstream Ganges River environment. These findings highlight that WWTPs may serve as potential hotspots for the dissemination of ARB and ARGs into the freshwater ecosystems, underscoring the urgent need for advanced treatment and monitoring strategies to mitigate antibiotic resistance spread.