Wastewater plants identified as ‘superspreaders’ of drug-resistant genes
Stellenbosch University researchers warn that local wastewater treatment plants act as reservoirs for high-risk genes that bypass current cleaning processes to reach our rivers.
Wastewater treatment plants across South Africa may be acting as ‘superspreaders’ of drug-resistant genetic material, raising fears over water security and public health.
A new study by Stellenbosch University (SU) found that even when bacteria are killed during treatment, their ‘extracellular DNA’ remains in the water. This genetic material carries high-risk antimicrobial resistance (AMR) genes into connected river systems.
Medical microbiologist Dr John Paul Makumbi says that while antibiotic resistance occurs naturally, the process is accelerated in treatment plants. These facilities become a ‘toxic melting pot’ where untreated waste from abattoirs, hospitals, and industry mixes with raw sewage.
“Even though the bacteria themselves are killed, we found extracellular DNA carrying resistant genes in the effluent,” says Makumbi. “These genes could still be transmitted and shared with other bacteria in the environment.”
The research, published in the journal Cell Reports this week, focused on nine plants and rivers in Tshwane. Scientists identified genetic material from two major bacterial groups, Pseudomonadota and Bacteroidota, both of which are known for multi-drug-resistant behaviour.
AMR is the ability of microbes to withstand medical treatments. If current trends continue, experts estimate that deaths from AMR will rise to 10 million people per year by 2050.
Most older South African treatment plants were designed to remove chemicals and kill live bacteria, but they cannot filter out this ‘free-floating’ DNA. Makumbi argues that to protect the public from ‘superbugs’, the country must upgrade its infrastructure and pretreat waste from high-risk sources like hospitals before it enters the municipal system.
Professor Thulani Makhlanyane, who holds the DSTI-NRF (Department of Science, Technology and Innovation – National Research Foundation) research chair in African Microbiome Innovation, warns that future conflicts will be tied to water security.
“This is especially true in Africa where ageing infrastructure, poor management, and an inability to sufficiently integrate science into policymaking is compounding the problem,” Makhlanyane says.
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