Antibiotic resistance is increasingly recognized as a major public health and environmental challenge, yet the risks are not evenly distributed across aquatic environments. A new study published in Biocontaminant finds that river-type drinking water sources generally carry higher risks from antibiotics, antibiotic resistance genes, and resistant bacteria than reservoir-type sources, highlighting the importance of considering water source type when designing monitoring and pollution-control strategies.
"Our results show that the type of water source is not simply a geographic label. It can influence how antibiotics and resistance genes enter, persist, and spread through aquatic environments," said corresponding author Huijun Ding of Nanchang University. "Identifying these differences can help water managers focus monitoring and prevention efforts on sources facing the greatest pressure."
The researchers investigated 13 representative drinking water sources across the Poyang Lake basin, which provides drinking water resources for approximately 45 million people. The sites included eight river-type sources and five reservoir-type sources and covered the five major rivers flowing into Poyang Lake as well as the lake itself. Samples were collected during winter and summer to capture different hydrological conditions.
The team screened for 46 antibiotics and detected 13. Florfenicol was the most frequently detected antibiotic, reaching concentrations of up to 72.85 nanograms per liter, while sulfamethoxazole reached up to 30.51 nanograms per liter. Source analysis suggested that antibiotic contamination was associated mainly with livestock farming, domestic sewage, and aquaculture, with substantial spatial differences across the basin.
Ecological risk assessment revealed that ciprofloxacin, norfloxacin, and erythromycin reached moderate to high risk levels at some sites in the Gan River sub-basin. At one upstream site, risk quotients reached 1.79 for ciprofloxacin and 1.31 for norfloxacin, while erythromycin reached 1.17 at a downstream site.
The study also examined antibiotic resistance genes, or ARGs. All targeted resistance-related genes were detected at every sampling site during summer, and sulfonamide resistance genes were the dominant group. Statistical modeling indicated that ARG abundance was strongly associated with mobile genetic elements, which can facilitate the transfer of resistance genes between microorganisms, as well as with water source type. Seasonal changes appeared to influence resistance indirectly by promoting this gene-transfer process.
To connect genetic evidence with actual bacterial resistance, the researchers isolated 178 bacterial strains from the water samples. The highest resistance rates were observed for lincomycin at 75.84% and penicillin at 53.95%. River-derived isolates also showed significantly greater resistance to these two antibiotics than reservoir-derived isolates.
A notable exception was Poyang Lake itself. Although classified with the reservoir-type sources in the study, its rapid water exchange and exposure to multiple pollution inputs resulted in resistance risks comparable to those observed in river sources.
The findings suggest that river-type drinking water sources and Poyang Lake should receive priority attention in basin-scale antimicrobial resistance surveillance. The authors also emphasize that monitoring programs should integrate antibiotic residues, resistance genes, and resistant bacteria rather than assessing each component separately.
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Journal reference: Zhang M, Xie X, Xu G, Yu J, Zhou W, et al. 2026. Key role of water source type in the risk of antibiotics, resistance genes, and resistance phenotypes in drinking water source at the basin scale. Biocontaminant 2: e013 doi: 10.48130/biocontam-0026-0010
https://www.maxapress.com/article/doi/10.48130/biocontam-0026-0010
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About Biocontaminant :
Biocontaminant (e-ISSN: 3070-359X) is a multidisciplinary platform dedicated to advancing fundamental and applied research on biological contaminants across diverse environments and systems. The journal serves as an innovative, efficient, and professional forum for global researchers to disseminate findings in this rapidly evolving field.
