Aquatic environments can act as reservoirs and transmission routes for antibiotic resistance genes, especially as resistance continues to grow. Hospital wastewater gets a bad rap because it can contain antibiotics, resistant bacteria, and resistance genes of clinical relevance.
However, a new study has shown that geography, rather than hospital proximity, primarily shapes resistance gene profiles.
In the study, published in Biocontaminant, Rong Zhang and Liguan Li's team at The Second Affiliated Hospital of Zhejiang University and The Education University of Hong Kong collected 100 surface water samples from rivers and lakes near hospitals in 11 Chinese cities, including sites within 500 meters and 500 to 2,000 meters downstream. For comparison, the researchers also sampled 21 sites in Nepal, including hospital-adjacent waters and untreated hospital wastewater, along with previously published data from rivers in mainland China, Hong Kong, South Korea and Switzerland.
Each 500 milliliter sample was filtered and DNA sequenced. Bioinformatic pipelines measured antibiotic resistance genes against a reference database, tracked mobile genetic elements, profiled microbial communities and reconstructed genomes from the sequencing data. The team then compared resistance gene patterns across cities, hospital types, sampling distances, water body types and regions.
Across Chinese hospital-adjacent waters, average antibiotic resistance gene abundance measured 0.47 copies per microbial cell, with samples containing an average of 389 gene subtypes. Shenzhen showed the highest abundance—nearly 8x that of Wuhan, the lowest—while Kunming had the greatest diversity of resistance genes.
Despite these differences, a shared set of core genes accounted for more than 96% of total resistance gene abundance in individual samples. Neither distance from a hospital nor hospital type meaningfully shifted the resistome—location was the dominant factor. Chinese hospital adjacent waters closely resembled typical rivers elsewhere in China and other regions, while hospital adjacent rivers in Nepal showed substantially higher resistance gene levels, consistent with weaker wastewater treatment.
The findings suggest hospitals don't automatically become major sources of antibiotic resistance in surrounding waters when medical wastewater is properly collected, treated and discharged under enforceable standards.
By linking environmental surveillance data to wastewater management conditions, the researchers say their approach offers a practical framework for identifying at-risk regions, evaluating treatment policies and prioritizing investment to curb the spread of resistance genes.
Data from Chinese Academy of Sciences