Antibiotic resistance is no longer confined to hospitals or clinics. Resistance genes that allow bacteria to withstand antibiotics are now routinely detected in rivers, lakes, soils, wildlife, livestock, and human communities. Because hospital wastewater can contain antibiotics, resistant bacteria, and genetic material capable of spreading resistance, hospitals are often viewed as major environmental sources. A new China-wide study, however, suggests that the influence of hospitals on nearby surface waters may be far more limited when wastewater treatment systems and discharge regulations are properly implemented.

Published in Biocontaminant, the study examined the resistomes of surface waters located downstream from hospitals in 11 Chinese cities. A resistome is the complete collection of antibiotic resistance genes, or ARGs, present in a microbial community. These genes can occur in bacteria that cause disease, but they may also be carried by harmless environmental microorganisms. Through processes such as horizontal gene transfer, ARGs can move between bacteria, potentially allowing resistance traits to spread through ecosystems and into human or animal populations.

The researchers collected 100 surface-water samples from Beijing, Shanghai, Shenzhen, Hangzhou, Tianjin, Wuhan, Hefei, Suzhou, Nanning, Kunming, and Baoding. Each sampling location was situated within 1,000 meters downstream of a hospital. To determine whether hospitals were shaping the surrounding microbial environment, the team also analyzed waters without a hospital within 2,000 meters and compared the Chinese results with river metagenomic datasets from mainland China, Hong Kong, South Korea, Switzerland, and Nepal.

The investigation relied on metagenomic sequencing, a technique that reads genetic material extracted directly from environmental samples rather than requiring individual bacteria to be isolated and grown in the laboratory. This approach allowed the researchers to identify resistance genes, mobile genetic elements, and the bacterial groups that might host them. The team then compared the abundance and composition of ARGs across cities, hospital types, hospital sizes, and distances from hospital discharge zones.

Resistance levels varied substantially among the Chinese cities. Shenzhen recorded the highest average ARG abundance, while Wuhan showed the lowest. Across all hospital-adjacent samples, the average was 0.47 ARG copies per bacterial cell, and each sample contained an average of 389 ARG subtypes. Although the overall resistome differed geographically, 12 major resistance categories accounted for more than 96 percent of the detected ARG abundance. These included genes associated with resistance to beta-lactam antibiotics, aminoglycosides, sulfonamides, tetracyclines, polymyxins, and several other drug classes.

The most significant result was that hospital characteristics did not appear to be the primary force determining the resistome of nearby waters. Surface waters beside large hospitals were not significantly different from those near small or medium-sized facilities. The researchers also found no meaningful distinction between waters downstream from general hospitals and those near specialized hospitals. Sampling distance had little influence as well: samples taken within 500 meters of a hospital were broadly similar to those collected between 500 and 1,000 meters downstream.

The study likewise found no significant difference in total ARG abundance between water bodies near hospitals and those with no hospital within 2,000 meters. Instead, geographic location and city-level environmental conditions were much stronger predictors of resistome composition. Differences in urban wastewater systems, population density, industrial activity, agricultural runoff, hydrology, antibiotic use, and background pollution may all contribute to these regional patterns. In other words, the broader urban environment appeared to matter more than the presence or size of an individual hospital.

A comparison with Nepal illustrated how wastewater infrastructure can influence environmental resistance levels. Hospital-adjacent rivers in the Nepalese dataset contained an average of 2.60 ARG copies per bacterial cell—more than five times the average measured in comparable Chinese rivers—and displayed substantially greater ARG diversity. The researchers emphasize that the comparison involved only two regions and should therefore be interpreted cautiously. Nevertheless, they suggest that limited wastewater treatment, inadequate sanitation, and widespread urban contamination may help explain the higher levels observed in Nepal.

The findings do not mean that hospital wastewater is harmless or that antibiotic resistance is no longer an environmental threat. The Chinese samples still contained high-risk ARGs, mobile genetic elements, and potential bacterial hosts capable of carrying resistance determinants. Mobile genetic elements, including plasmids and other DNA structures, are especially important because they can facilitate the transfer of ARGs between unrelated bacteria. The presence of these elements means that even moderate environmental resistance levels deserve continued monitoring, particularly in waterways used for recreation, irrigation, drinking-water production, or aquaculture.

The researchers conclude that effective wastewater treatment, strict discharge controls, sanitation infrastructure, and routine environmental surveillance should be developed as interconnected measures. Their results suggest that hospitals do not inevitably cause severe resistance pollution in surrounding rivers when treatment and regulatory systems function effectively. At the same time, the study points to a broader challenge: controlling environmental antibiotic resistance will require attention not only to hospitals, but also to municipal wastewater, agriculture, industrial discharges, urban development, and antibiotic consumption. For countries seeking cost-effective strategies to slow the spread of resistance, the findings offer evidence that strong containment systems can significantly limit the environmental release of hospital-associated ARGs.

Subject of Research: The influence of hospital wastewater and wastewater-management practices on antibiotic resistance genes in adjacent surface waters.

Article Title: What leaves the hospitals can be contained: a China-wide resistome study reveals limited impact of hospitals on adjacent surface waters

News Publication Date: 26-Jun-2026

Web References: Biocontaminant: https://www.maxapress.com/biocontam; DOI: https://doi.org/10.48130/biocontam-0026-0008

References: Ju X, Gai W, Yan Z, Wu Z, Sun Y, et al. 2026. “What leaves the hospitals can be contained: a China-wide resistome study reveals limited impact of hospitals on adjacent surface waters.” Biocontaminant 2: e011. doi:10.48130/biocontam-0026-0008

Image Credits: Xiaoyang Ju, Wudi Gai, Zelin Yan, Yuchen Wu, Yi Sun, Hanyu Wang, Haicai Cheng, Yuxin Tao, Guhang Shi, Xuemei Mao, Yanping Mao, Ke Yu, Tong Zhang, Rong Zhang, and Liguan Li

Keywords

Antibiotic resistance, antimicrobial resistance, resistance genes, ARGs, resistome, hospital wastewater, wastewater treatment, surface water, metagenomics, environmental microbiology, public health, water pollution, mobile genetic elements, China-wide study, environmental surveillance

Tags: and exploring horizontal gene transfer of ARGs among bacteria in aquatic ecosystemsantibiotic resistance in nearby watershighlighting the impact of wastewater treatment and discharge regulations on environmental resistome levelsthe study analyzed the presence and diversity of antibiotic resistance genes