Central London’s freshwater sources contain high levels of antibiotic resistant genes, with the River Thames having the highest amount, according to research by UCL.
The Regent’s Canal, Regent’s Park Pond and the Serpentine all contained the genes but at lower levels than the Thames, which contained genes providing resistance for bacteria to common antibiotics such as penicillin, erythromycin and tetracycline.
The genes come from bacteria in human and animal waste. When antibiotics are taken by humans much of the drug is excreted into the sewer system and then into freshwater sources. The presence of antibiotics in these water sources provides an environment where microbes carrying the resistance genes can multiply quicker and share their resistance with other microbes.
Project lead Dr. Lena Ciric (UCL Civil, Environmental & Geomatic Engineering) said: “This shows that more research is needed into the efficiency of different water treatment methods for a The Thames is likely to have higher levels of antibiotics and resistant genes because a large number of wastewater treatment works discharge into it both upstream and in London.
Antibiotics entering the sewer system are diluted through flushing, but even low levels can encourage resistance genes to multiply and spread to more microbes.
The research team developed a DNA-based method which can provide information about the number of each of the resistant genes per litre of water. They then compared the numbers of the resistant genes in the different London water systems.
ntibiotic removal, as none of the treatments currently used were designed to incorporate this.
There is currently no legislation to remove antibiotics or the resistant genes from water sources, implying that antibiotics and the resistant genes could be present in small amounts in drinking water, although this would require testing.