Proper wastewater treatment can reduce the impact of hospitals on surrounding waters

Antibiotic resistance genes are now widely found in rivers, lakes, soils, animals, and people. Hospitals are often considered important sources because their wastewater can contain antibiotics, drug-resistant bacteria, and resistance genes. However, a nationwide study suggests that proper wastewater treatment and strict discharge controls can substantially reduce the impact of hospitals on surrounding water environments.

Researchers examined surface waters near hospitals in 11 Chinese cities and found that the abundance and composition of antibiotic resistance genes, or ARGs, were influenced more strongly by geographic location than by the presence, size, or type of a nearby hospital.

Our findings show that hospital wastewater does not inevitably lead to severe antibiotic resistance pollution in surrounding rivers. When treatment infrastructure and discharge policies are properly implemented, the environmental release of resistance genes from hospitals can be effectively contained."

Liguan Li, corresponding author

The team collected 100 hospital-adjacent surface water samples from Beijing, Shanghai, Shenzhen, Hangzhou, Tianjin, Wuhan, Hefei, Suzhou, Nanning, Kunming, and Baoding. Sampling sites were located within 1,000 meters downstream of hospitals. The researchers also analyzed non-hospital-adjacent waters and compared their results with river metagenomic datasets from mainland China, Hong Kong, South Korea, Switzerland, and Nepal.

Using metagenomic sequencing, the researchers measured the complete collection of resistance genes, known as the resistome, in each sample.

ARG abundance varied widely among the Chinese cities. Shenzhen had the highest average abundance, while Wuhan had the lowest. Across all hospital-adjacent samples, the average abundance was 0.47 ARG copies per bacterial cell, and researchers identified an average of 389 ARG subtypes.

Despite differences among locations, 12 core resistance categories accounted for more than 96 percent of total ARG abundance. These included genes associated with resistance to beta-lactams, aminoglycosides, sulfonamides, tetracyclines, polymyxins, and several other antibiotic classes.

Importantly, hospital characteristics did not significantly shape nearby water resistomes. Waters near large hospitals were not significantly different from those near small or medium hospitals. General and specialized hospitals also showed no significant differences. Sampling distance, whether within 500 meters or between 500 and 1,000 meters downstream, had little effect.

Similarly, the researchers found no significant difference in total ARG abundance between hospital-adjacent waters and waters with no hospital within 2,000 meters. Instead, the city where the sample was collected was a much stronger predictor of the resistome profile.

A comparison with Nepal highlighted the importance of wastewater management. Hospital-adjacent rivers in Nepal contained an average of 2.60 ARG copies per cell, more than five times the level measured in comparable Chinese rivers. The Nepalese samples also contained substantially greater ARG diversity. The authors caution that this comparison involved only two regions, but suggest that inadequate wastewater treatment and widespread urban pollution may contribute to the higher levels observed in Nepal.

The study also detected high-risk ARGs, mobile genetic elements, and potential pathogenic hosts in Chinese surface waters. These findings indicate that antibiotic resistance remains an environmental concern even when hospitals are not the dominant source.

The researchers conclude that hospital wastewater treatment, sanitation infrastructure, discharge regulation, and routine environmental surveillance should be developed together. The results may offer practical guidance for low- and middle-income countries seeking cost-effective ways to reduce the environmental spread of antibiotic resistance.